US20050062099A1 - Semiconductor device including multiple field effect transistors, with first fets having oxide spacers and the second fets having oxide nitride oxidation protection - Google Patents
Semiconductor device including multiple field effect transistors, with first fets having oxide spacers and the second fets having oxide nitride oxidation protectionDownload PDFInfo
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- US20050062099A1 US20050062099A1US10/981,537US98153704AUS2005062099A1US 20050062099 A1US20050062099 A1US 20050062099A1US 98153704 AUS98153704 AUS 98153704AUS 2005062099 A1US2005062099 A1US 2005062099A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
- H01L21/28008—Making conductor-insulator-semiconductor electrodes
- H01L21/28017—Making conductor-insulator-semiconductor electrodes the insulator being formed after the semiconductor body, the semiconductor being silicon
- H01L21/28247—Making conductor-insulator-semiconductor electrodes the insulator being formed after the semiconductor body, the semiconductor being silicon passivation or protection of the electrode, e.g. using re-oxidation
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10D64/00—Electrodes of devices having potential barriers
- H10D64/01—Manufacture or treatment
- H10D64/021—Manufacture or treatment using multiple gate spacer layers, e.g. bilayered sidewall spacers
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10D84/00—Integrated devices formed in or on semiconductor substrates that comprise only semiconducting layers, e.g. on Si wafers or on GaAs-on-Si wafers
- H10D84/01—Manufacture or treatment
- H10D84/0123—Integrating together multiple components covered by H10D12/00 or H10D30/00, e.g. integrating multiple IGBTs
- H10D84/0126—Integrating together multiple components covered by H10D12/00 or H10D30/00, e.g. integrating multiple IGBTs the components including insulated gates, e.g. IGFETs
- H10D84/0144—Manufacturing their gate insulating layers
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10D84/00—Integrated devices formed in or on semiconductor substrates that comprise only semiconducting layers, e.g. on Si wafers or on GaAs-on-Si wafers
- H10D84/01—Manufacture or treatment
- H10D84/0123—Integrating together multiple components covered by H10D12/00 or H10D30/00, e.g. integrating multiple IGBTs
- H10D84/0126—Integrating together multiple components covered by H10D12/00 or H10D30/00, e.g. integrating multiple IGBTs the components including insulated gates, e.g. IGFETs
- H10D84/0147—Manufacturing their gate sidewall spacers
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10D84/00—Integrated devices formed in or on semiconductor substrates that comprise only semiconducting layers, e.g. on Si wafers or on GaAs-on-Si wafers
- H10D84/01—Manufacture or treatment
- H10D84/02—Manufacture or treatment characterised by using material-based technologies
- H10D84/03—Manufacture or treatment characterised by using material-based technologies using Group IV technology, e.g. silicon technology or silicon-carbide [SiC] technology
- H10D84/038—Manufacture or treatment characterised by using material-based technologies using Group IV technology, e.g. silicon technology or silicon-carbide [SiC] technology using silicon technology, e.g. SiGe
Definitions
- the present inventionrelates generally to semiconductor devices and manufacturing methods thereof, and more particularly, to a semiconductor device including a plurality of field effect transistors and a manufacturing method thereof.
- FIG. 79is a cross sectional view showing such a conventional 2-power supply semiconductor device including a plurality of field effect transistors.
- the conventional 2-power supply semiconductor deviceinclude a first field effect transistor supplied with first power supply voltage (low Vdd) and a second field effect transistor supplied with second power supply voltage (high Vdd) higher than low Vdd formed on a main surface of a p type semiconductor substrate 101 and spaced apart from each other.
- An isolation oxide film 102is formed between the first and second field effect transistors.
- a pair of first source/drain regions 110 and a pair of low concentration impurity diffusion regions 108are formed spaced apart from each other on the main surface of semiconductor substrate 101 having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 108 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 110 formed adjacent to n type impurity diffusion region 108constitute an LDD (Lightly Doped Drain) structure.
- a first gate insulating film 106is formed on the first channel region.
- a first gate electrode 118is formed on first gate insulating film 106 .
- a sidewall oxide film 109is formed on a side of first gate electrode 118 .
- the first field effect transistor supplied with low Vddis formed of first source/drain regions 110 , impurity diffusion regions 108 , first gate insulating film 106 , and first gate electrode 118 .
- a pair of second source/drain regions 117 and a pair of low concentration impurity diffusion regions 116are formed on the main surface of semiconductor substrate 101 , spaced apart from each other and having a second channel region therebetween.
- Second source/drain region 117 and low concentration impurity diffusion region 116in other words low concentration n type impurity diffusion region 116 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 117 formed adjacent to n type impurity diffusion region 116 constitute an LDD structure.
- a second gate insulating film 104is formed on the second channel region.
- First gate insulating film 106is formed on second gate insulating film 104 .
- a second gate electrode 119is formed on first gate insulating film 106 .
- a sidewall oxide film 120is formed on a side of second gate electrode 119 .
- Second source/drain regions 117 and impurity diffusion region 116 , second gate insulating film 104 , first gate insulating film 106 and first gate electrode 119form the second field effect transistor supplied with high Vdd.
- the gate insulating films 104 and 106 of the second field effect transistor supplied with high Vddshould be thicker than the first gate insulating film 106 of first field effect transistor supplied with low Vdd.
- Isolation oxide film 102is formed on the main surface of semiconductor substrate 101 to surround an active region.
- Second gate insulating film 104is formed on the active region on the main surface of semiconductor substrate 101 .
- a resist pattern 105 ais formed on second gate insulating film 104 positioned in the high Vdd region and on isolation oxide film 102 . The structure as shown in FIG. 80 is thus obtained.
- An isotropic etchingis performed using resist pattern 105 a as a mask to remove second gate insulating film 104 positioned in the low Vdd region to obtain the structure as shown in FIG. 81 . Resist pattern 105 a is then removed.
- first gate insulating film 106is formed on the main surface of semiconductor substrate 101 and on second gate insulating film 104 .
- a first doped polysilicon film 103(see FIG. 83 ) is deposited on first gate insulating film 106 and isolation oxide film 102 .
- Resist patterns 105 b and 105 care formed on the regions of first doped polysilicon film 103 to be first and second gate electrodes 118 and 119 (see FIG. 79 ). The structure as shown in FIG. 83 is thus obtained.
- first and second gate electrodes 118 and 119are formed as a result.
- Resist patterns 105 b and 105 care then removed.
- the structure as shown in FIG. 84is thus obtained.
- the gate insulating film portion of the second field effect transistor formed of first and second gate insulating films 106 and 104can be made thicker than the first gate insulating film 106 of the first field effect transistor.
- the breakdown voltage of the second field effect transistorcan be greater than the breakdown voltage of the first field effect transistor, so that the second field effect transistor may be supplied with voltage higher than the first field effect transistor.
- an n type impurityis introduced into a prescribed region of the main surface of semiconductor substrate 101 to form low concentration n type impurity diffusion regions 108 and 116 .
- Sidewall oxide films 109 and 120are formed on sides of first and second gate electrodes 118 and 119 .
- An n type impurityis then introduced into a prescribed region of the main surface of semiconductor substrate 101 to form high concentration n type impurity diffusion regions 110 and 117 as shown in FIG. 86 .
- the conventional 2-power supply semiconductor deviceis manufactured as described above.
- resist pattern 105 ais directly formed on second gate insulating film 104 positioned in the high Vdd region.
- defectslocal irregularities
- a light etching processing for removing resist pattern 105 ais directly performed to the surface of second gate insulating film 104 , second gate insulating film 104 may be reduced in thickness.
- the defects in the surface of second gate insulating film 104 and the reduction in thicknesslead to a reduction in the breakdown voltage of second gate insulating film 104 , and as a result electrical characteristics of the semiconductor device including the field effect transistor deteriorate.
- FIGS. 87 to 93As a countermeasure, a manufacturing method as shown in FIGS. 87 to 93 has been proposed.
- Isolation oxide film 102is formed on the main surface of p type semiconductor substrate 101 to surround an active region.
- Second gate insulating film 104is formed on the active region in the main surface of p type semiconductor substrate 101 .
- First doped polysilicon film 103is formed on second gate insulating film 104 and isolation oxide film 102 .
- Resist pattern 105 ais formed on the region of first doped polysilicon film 103 to be second gate electrode 119 (see FIG. 88 ) positioned in the high Vdd region to obtain the structure as shown in FIG. 87 .
- resist pattern 105 ais then removed.
- Resist pattern 105 bis formed on second gate insulating film 104 positioned in the high Vdd region and second gate electrode 119 to form the structure as shown in FIG. 88 .
- second gate electrode 119is formed on second gate insulating film 104 and then resist pattern 105 b is formed. Resist pattern 105 b is not directly formed on the region of the surface of second gate insulating film 104 in contact with second gate electrode 119 . Thus, defects in the surface of second gate insulating film 104 as in the manufacturing method shown in FIGS. 80 to 86 can be prevented.
- second gate insulating film 104 positioned in the low Vdd regionis removed by an isotropic etching. Then, resist pattern 105 b is removed.
- a silicon oxide film to be first gate insulating film 106is formed on the main surface of p type semiconductor substrate 101 positioned in the low Vdd region and on second gate insulating film 104 and second gate electrode 119 .
- first gate insulating film 106 and isolation oxide film 102a second doped polysilicon film 107 (see FIG. 91 ) is formed by means of CVD.
- Resist pattern 105 cis formed on the region of second doped polysilicon film 107 to be first gate electrode 118 (see FIG. 93 ). The structure as shown in FIG. 91 is thus obtained.
- An anisotropic etchingis performed using resist pattern 105 c as a mask to remove a part of second doped polysilicon film 107 , and first gate electrode 118 (see FIG. 92 ) is formed as a result. After the anisotropic etching, a part of second doped polysilicon film 107 also remains on a side of second gate electrode 119 . Resist pattern 105 c is then removed. Resist pattern 105 d (see FIG. 92 ) is formed on first gate insulating film 106 positioned in the low Vdd region and on first gate electrode 118 . Thus, the structure as shown in FIG. 92 results.
- Second doped polysilicon film 107 remaining on the side of second gate electrodeis removed by an isotropic etching, and then resist pattern 105 d is removed.
- n type impurity diffusion regions 108 , 116are formed by introducing an impurity, sidewall oxide films 109 , 120 (see FIG. 93 ) are formed, followed by formation of high concentration n type impurity diffusion regions 110 , 117 (see FIG. 93 ), and the semiconductor device as shown in FIG. 93 results.
- second gate electrode 119is formed before resist pattern 105 b is formed as shown in FIG. 88 , in order to prevent defects from being formed in the surface of second gate insulating film 104 .
- second gate electrode 119 formed of doped polysiliconis oxidized in an end 123 of the contact portion between second gate electrode 119 and second gate insulating film 104 as shown in FIG. 94 . Therefore, a silicon oxide film 124 grows along the contact surface between second gate insulating film 104 and second gate electrode 119 .
- FIG. 94is an enlarged view of region 110 shown in FIG. 90 .
- the gate oxide film having a “gate bird's beak” formed of an oxide filmis poor in quality and difficult to control in thickness. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors deteriorate.
- the present inventionis directed to a solution to the above-described problems. It is one object of the invention to provide a semiconductor device which can prevent electrical characteristics of the device from deteriorating by preventing the deterioration of the quality of a gate insulating film.
- Another object of the inventionis to provide a semiconductor device which can prevent a gate bird's beak from being generated.
- Yet another object of the inventionis to provide a method of manufacturing a semiconductor device which can prevent the deterioration of the quality of a gate insulating film.
- a semiconductor devicehaving a plurality of field effect transistors includes first and second field effect transistors.
- the first field effect transistorincludes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode.
- the second field effect transistorincludes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode.
- the first source/drain regionsare formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween.
- the first gate insulating filmis formed on the first channel region in a first thickness.
- the second source/drain regionsare formed on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween.
- the second gate insulating filmis formed on the second channel region in a second thickness larger than the first thickness.
- the second gate electrodeis formed on the second gate insulating film.
- An oxidation protection film to prevent one of the first and second gate electrodes from being oxidizedis formed on a side of one of the gate electrodes.
- the oxidation protection film to prevent the gate electrode from being oxidizedis formed on a side of one of the first and second gate electrodes, and therefore an oxidizing step to form a gate insulating film of another field effect transistor may be performed while the oxidization protection film is formed on a side of that one gate electrode.
- the lower part of the side of the gate electrodecan be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- a semiconductor devicehaving a plurality of field effect transistors includes first and second field effect transistors.
- the first field effect transistorincludes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode.
- the second field effect transistorincludes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode.
- the first source/drain regionsare formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween.
- the first gate insulating filmhas a first thickness and is formed on the first channel region to include an oxide nitride film.
- the first gate electrodeis formed on the first gate insulating film.
- the second source/drain regionsare formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween.
- the second gate insulating filmis formed on the second channel region and has a second thickness larger than the first thickness.
- the second gate electrodeis formed on the second gate insulating film.
- the first gate insulating filmis formed to include the oxide nitride film, in the manufacturing process which will be described, in the presence of the second gate electrode, during forming the oxide nitride film to be the first gate insulating film, an end of the second gate electrode can be prevented from being excessively oxidized in the contact portion between a lower part of a side of the second gate electrode and the second gate insulating film.
- the lower part of the side of the gate electrodecan be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- the first gate insulating filmis formed to include the oxide nitride film, the first gate insulating film may be formed thinner with a prescribed breakdown voltage being maintained than the case of using a conventional silicon oxide film or the like. As a result, the driving voltage of the first field effect transistor may be reduced.
- a semiconductor devicehaving a plurality of field effect transistors includes first and second field effect transistors.
- the first field effect transistorincludes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode.
- the second field effect transistorincludes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode.
- the first source/drain regionsare formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween.
- the first gate insulating filmis formed on the first channel region and has a first thickness.
- the first gate electrodeis formed on the first gate insulating film.
- the second source/drain regionsare formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween.
- the gate insulating filmis formed on the second channel region and has a second thickness larger than the first thickness.
- the second gate electrodeis formed on the second gate insulating film.
- An anti-oxidation conductive filmis formed on at least one of the first and second gate insulating films.
- the anti-oxidation conductive filmis formed on at least one of the first and second gate insulating films, it is not necessary to form a resist pattern directly on the surface of one of the first and second gate insulating films in the following manufacturing steps. Furthermore, before forming one of the first and second gate electrodes, an oxidizing step to form the other one of the first and second gate insulating films may be performed using the anti oxidation conductive film. Thus, in the step of oxidizing the first gate insulating film, a lower part of the side of one of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- the anti-oxidation conductive filmis formed on one of the first and second gate insulating films, a resist pattern will not be formed directly on one of the first and second gate insulating films in the following manufacturing steps. As a result, defects such as local irregularities in the gate insulating film as formed during removing the resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating.
- a semiconductor film having a conductive impuritymay be formed at a position between the anti-oxidation conductive film and at least one of the first and second gate insulating films.
- a semiconductor devicehaving a plurality of field effect transistors includes first and second field effect transistors.
- the first field effect transistorincludes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode.
- the second field effect transistorincludes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode.
- the first source/drain regionsare formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween.
- the first gate insulating filmis formed on the first channel region and has a first thickness.
- the first gate electrodeis formed on the first gate insulating film.
- the second source/drain regionsare formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween.
- the second gate insulating filmis formed on the second channel region and has a second thickness.
- the second gate electrodeis formed on the second gate insulating film.
- a semiconductor film having a conductive impurityis formed on and in contact with at least one of the first and second gate insulating films.
- An anti-oxidation insulating film for preventing the semiconductor film having the conductive impurity from being oxidizedis formed on the semiconductor film.
- the semiconductor film having the conductive impurityis thus formed on and in contact with one of the first and second gate insulating films, it is not necessary to form a resist pattern directly on a surface of one of the first and second gate insulating films in the manufacture of the semiconductor device.
- an oxidizing step to form the other one of the first and second gate insulating filmsmay be performed using the anti-oxidation insulating film as a mask.
- a lower part of a side of the gate electrodescan be prevented from being oxidized as a result, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the semiconductor film having the conductive impurityis formed on and in contact with one of the first and second gate insulating films, a resist pattern is not formed directly on one of the first and second gate insulating films.
- defectssuch as local irregularities in the gate insulating films as formed during removing the resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating.
- the formation of a depletion layer caused by a reduction in the concentration of the conductive impurity in the vicinity of one of the first and second gate insulating filmsmay be prevented.
- the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layercan be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- a semiconductor devicehaving a plurality of field effect transistors includes first and second field effect transistors.
- the first field effect transistorincludes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode.
- the second field effect transistorincludes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode.
- the second gate electrodehas a first conductive film, an insulating film and a second conductive film.
- the first source/drain regionsare formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween.
- the first gate insulating filmis formed on the first channel region and has a first thickness.
- the first gate electrodeis formed on the first gate insulating film.
- the second source/drain regionsare formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween.
- the second gate insulating filmis formed on the second channel region and has a second thickness.
- the first conductive film to be a part of the second gate electrodeis formed on the second gate insulating film.
- the insulating film to be a part of the second gate electrodeis formed on the first conductive film.
- the second conductive film to be a part of the second gate electrodeis formed on the insulating film.
- the second gate electrodehas the first conductive film, the insulating film, and the second conductive film, and therefore an oxidizing step for forming the first gate insulating film can be performed before forming the second gate electrode without forming a resist pattern directly on the surface of the second gate insulating film.
- an oxidizing step for forming the first gate insulating filmcan be performed before forming the second gate electrode without forming a resist pattern directly on the surface of the second gate insulating film.
- a lower part of a side of the gate electrodecan be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- a semiconductor devicehaving a plurality of field effect transistors includes first and second field effect transistors.
- the first field effect transistorincludes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode.
- the second field effect transistorincludes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode.
- the first source/drain regionsare formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween.
- the first gate insulating filmis formed on the first channel region and has a first thickness.
- the first gate electrodeis formed on the first gate insulating film.
- the second source/drain regionsare formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween.
- the second gate insulating filmis formed on the second channel region and has a second thickness larger than the first thickness.
- the second gate electrodeis formed on the second gate insulating film.
- a protection conductive filmis formed on and in contact with at least one of the first and second gate insulating films.
- the protection conductive filmis formed on and in, contact with one of the first and second gate insulating films, it is not necessary to form a resist pattern directly on the surface of one of the first and second gate insulating films. Furthermore, before forming one of the first and second gate electrodes, an oxidizing step for forming the other one of the first and second gate insulating films can be performed using the protection conductive film. Thus, in the step of oxidizing the gate insulating films, a lower part of a side of one of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- the protection conductive filmincludes first and second protection conductive films.
- the first protection conductive filmmay be formed on and in contact with the first gate insulating film, while the second protection conductive film may be formed on and in contact with the second gate insulating film.
- the first and second protection conductive filmsmay be substantially equal in thickness.
- the part of the thickness of the first and second protection conductive films to be removed by the etchingcan be made substantially equal in the regions to form the first and second gate electrodes.
- the amount of etching for forming the first gate electrodecan be substantially the same as the amount of etching for forming the second gate electrode. Therefore, the amount of overetching during forming the first and second gate electrodes can be reduced.
- the semiconductor substrate or the like positioned under the protection conductive films to be etched awaycan be prevented from being damaged by overetching.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the semiconductor devicemay further include a protection conductive film formed by depositing a film having an amorphous structure.
- the film having the amorphous structureis free from grain boundaries, and therefore during isotropically etching the protection conductive film in the manufacture of the semiconductor device, damages to the gate insulating film positioned under the protection conductive film caused by the isotropic etching agent running along grain boundaries can be prevented.
- the fluctuation of the threshold voltages of the field effect transistorscan be prevented.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented.
- an anti-oxidation filmmay be formed on and in contact with the protection conductive film.
- a natural oxide film difficult to control in thicknesscan be prevented from being formed on the protection conductive film.
- the variation of the thickness of the protection conductive film to be etched away caused by the formation of such a natural oxide filmcan be prevented.
- the variation of the thickness of the protection conductive film to be etched awaycan be reduced, the amount of overetching, can be reduced.
- damages to the semiconductor substrate or the like positioned under the protection conductive film to be etched away, caused by overetchingcan be prevented.
- a first gate insulating film having a first thicknessis formed on a main surface of a semiconductor device.
- a first gate electrodeis formed on the first gate insulating film.
- an impurityis introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween.
- a second gate insulating film having a second thickness larger than the first thicknessis formed on the main surface of the semiconductor substrate.
- an impurityis introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween.
- An oxidation protection film to prevent a gate electrode from being oxidizedis formed on a side of one of the first and second gate electrodes. After one of the first and second gate insulating films is formed, the other one of the first and second gate insulating films is formed with the oxidation protection film being present on the side of the gate electrode formed on that one of the first and second gate insulating films.
- the gate electrodebeing formed on one of the first and second gate insulating films
- the other one of the first and second gate insulating filmsis formed, and therefore resist pattern is not directly formed on the gate insulating film. Therefore, during the following removal of the resist pattern, a direct light etching processing can be prevented on the surface of the gate insulating film. As a result, defects in the surface of the gate insulating film caused by such a light etching processing can be prevented.
- the oxidation protection film for preventing a gate electrode from being oxidizedbeing present on a side of one of the first and second gate electrodes, an oxidizing step to form the other one of the first and second gate insulating films is performed.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- a first gate insulating film including an oxide nitride film and having a first thicknessis formed on a main surface of a semiconductor substrate.
- a first gate electrodeis formed on the first gate insulating film.
- an impurityis introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween.
- a second gate insulating film having a second thickness larger than the first thicknessis formed on the main surface of the semiconductor substrate.
- an impurityis introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween.
- the first gate insulating filmis formed in the presence of the second gate electrode formed on the second gate insulating film.
- the first gate insulating filmis formed, and therefore resist pattern is not directly formed on the second gate insulating film. Therefore, during the following removal of the resist pattern, a direct light etching processing on the surface of the second gate insulating films can be prevented. Thus, defects in the surface of the second gate insulating film caused by such a light etching processing can be prevented.
- the step of forming the first gate insulating film to include the oxide nitride filmsince there is the step of forming the first gate insulating film to include the oxide nitride film, an end of the second gate electrode can be suppressed from being excessively oxidized at the joint of a lower part of a side of the second gate electrode and the second gate insulating film during forming the oxide nitride film to be the first gate insulating film while the second gate electrode has been formed.
- a gate bird's beakcan be avoided. Therefore, the threshold voltages of the field effect transistors can be prevented increasing, and as a result electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- the first gate insulating filmis formed to include the oxide nitride film, the thickness of the first gate insulating film can be made smaller than the case of using a conventional silicon oxide film as a prescribed breakdown voltage is maintained. As a result, the driving voltage of the first field effect transistor can be reduced.
- a first gate insulating film having a first thicknessis formed on a main surface of a semiconductor substrate.
- a first gate electrodeis formed on the first gate insulating film.
- an impurityis introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween.
- a second gate insulating film having a second thickness larger than the first thicknessis formed on the main surface of the semiconductor substrate.
- an impurityis introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween.
- An anti-oxidation conductive filmis formed on at least one of the first and second gate insulating films. While the anti-oxidation conductive film has been formed on at least one of the first and second gate insulating films, the other one of the first and second gate insulating films is formed.
- the anti-oxidation conductive filmis formed on one of the first and second gate insulating films, it is not necessary to directly form a resist pattern on the surface of one of the first and second gate insulating films.
- an oxidizing step to form the other one of the first and second gate insulating filmscan be performed using the anti-oxidation conductive film as a mask.
- a lower part of a side of one of the first and second gate electrodescan be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the anti-oxidation conductive filmis formed on one of the first and second gate insulating films, a resist pattern is not directly formed on that one of the first and second gate insulating films. As a result, defects such as local irregularities in the gate insulating film as formed during removing a resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating.
- the method of manufacturing the semiconductor devicemay further include the step of forming a semiconductor film including a conductive impurity at a position between the anti-oxidation conductive film and at least one of the first and second gate insulating films.
- a substrate protection filmmay be formed in the region on the main surface of the semiconductor substrate to form one of the first and second gate insulating films. With the substrate protection film being present, the other one of the first and second gate insulating films and the anti-oxidation conductive film may be formed.
- the insulating film forming the other one of the first and second gate insulating filmcan be prevented from being formed in contact with the main surface of the semiconductor substrate positioned in the region to form one of the first and second gate insulating films.
- the main surface of the semiconductor substrate positioned in the region to form that one of the first and second gate insulating filmscan be prevented from being directly etched.
- damages to the main surface of the semiconductor substrate caused by etchingcan be prevented.
- the deterioration of the quality of one of the first and second gate insulating films caused by the presence of damages by the etching on the main surface of the semiconductor substrate in which the gate insulating film is formedcan be prevented.
- the fluctuation of the threshold voltage of the field effect transistorscan be prevented.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented.
- the method of manufacturing the semiconductor device according to this aspectmay further include the step of removing a part of the main surface of the semiconductor substrate positioned in the region to form one of the first and second gate insulating films before forming that insulating film.
- the main surface of the semiconductor substrate positioned in the region to form one of the first and second gate insulating films by means of etching in the manufacture of the semiconductor devicea part of the main surface of the semiconductor substrate with damages such as local irregularities can be removed. Therefore, that one of the first and second gate insulating films can be formed on the main surface of the semiconductor substrate removed of the damaged part. Therefore, the quality of the gate insulating film can be prevented from deteriorating due to damages on the main surface of the semiconductor substrate.
- the fluctuation of the threshold voltages of the field effect transistorscan be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented.
- a first gate insulating film having a first thicknessis formed on a main surface of a semiconductor device.
- a first gate electrodeis formed on the first gate insulating film.
- an impurityis introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween.
- a second gate insulating film having a second thickness larger than the first thicknessis formed on the main surface of the semiconductor substrate.
- a first conductive film to be a part of a second electrodeis formed on the second gate insulating film.
- An insulating film to be a part of the second gate electrodeis formed on the first conductive film.
- a second conductive film to be a part of the second gate electrodeis formed on the insulating film.
- the first and second insulating films and the insulating filmare anisotropically etched to form the second gate electrode.
- an impurityis introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween.
- the first gate insulating filmis formed in the presence of the first conductive film.
- the first gate insulating filmis formed, and therefore an oxidizing step to form the first gate insulating film can be performed without forming a resist pattern directly on the surface of the second gate insulating film. Therefore, during the following removal of the resist pattern, a direct light etching processing to the surface of the second gate insulating film can be prevented. Thus, defects on the surface of the second gate insulating film caused by such a light etching processing can be prevented.
- the first and second conductive films and the insulating filmare anisotropically etched to form the second gate electrode, a side of the second gate electrode can be prevented from being oxidized in the oxidizing step to form the first gate insulating film.
- a gate bird's beakcan be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the insulating filmwhen a voltage is supplied to the second gate electrode, the voltage drops in the insulating film, and voltage imposed on the second gate insulating film can be reduced.
- a first gate insulating film having a first thicknessis formed on a main surface of a semiconductor substrate.
- a first gate electrodeis formed on the first gate insulating film.
- an impurityis introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween.
- a second gate insulating film having a second thickness larger than the first thicknessis formed on the main surface of the semiconductor substrate.
- a second gate electrodeis formed on the second gate insulating film.
- an impurityis introduced into the main surface of the substrate to form a pair of second source/drain regions, spaced apart from each other and having a second channel region therebetween.
- a protection conductive film for protecting a gate insulating filmis formed on and in contact with at least one of the first and second gate insulating films. While the protection conductive film has been formed, the other one of the first and second gate insulating films is formed.
- the protection conductive filmis formed on and in contact with one of the first and second gate insulating films, it is not necessary to directly form a resist pattern on that one of the first and second gate insulating films. Furthermore, before forming one of the first and second gate electrodes, an oxidizing step to form the other one of the first and second gate insulating films using the protection conductive film as a mask can be performed. As a result, a lower part of the side of one of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- a conductive filmmay be formed on and in contact with the other one of the first and second gate insulating films.
- a resist patternmay be formed on and in contact with the conductive film and the protection conductive film. Using the resist pattern as a mask, part of the conductive film and the protection conductive film is anisotropically etched away to simultaneously form the first gate electrode and the second gate electrode.
- the resist patternis formed on and in contact with the protection conductive film and the conductive film, part of the conductive film and the protection conductive film is anisotropically etched away using the resist pattern as a mask, and therefore the first and second gate electrodes can be formed only of the conductive film and the protection conductive film.
- an insulating filmis formed on a main surface of a semiconductor substrate positioned in regions to form first and second field effect transistors.
- a resist patternis formed on the insulating film positioned in the regions to form the second field effect transistor.
- a part of the insulating film positioned in the region to form the first field effect transistoris isotropically etched away, followed by removal of the resist pattern.
- a first gate electrodeis formed on the first gate insulating film.
- an impurityis introduced into the main surface of the semiconductor substrate to form a pair of source/drain regions, spaced apart from each other and having a first channel region therebetween.
- a second gate electrodeis formed on the second gate insulating film.
- an impurityis introduced into the main surface of the semiconductor substrate, to form a pair of second source/drain regions, spaced apart from each other and having a second channel region therebetween.
- the first and second gate insulating filmsare formed of a single insulating film, only a single oxidizing step is necessary to form the first and second gate insulating films. Since the first and second gate electrodes are formed after forming the first and second gate insulating films, thus first and second gate electrodes are not oxidized during forming the first and second gate insulating films. As a result, a lower part of a side of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- the process of manufacturing the semiconductor devicecan be simplified.
- the first and second gate insulating filmsare formed by means of isotropic etching, possible defects such as local irregularities caused by for example a step of ashing during removal of the resist pattern on the insulating film to be the first and second gate insulating films can be removed by the anisotropic etching.
- a defectless, highly reliable gate insulating filmmay be obtained, and the fluctuation of the threshold voltages of the field effect transistors can be prevented.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- FIG. 1is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a first embodiment of the invention
- FIGS. 2 to 10are cross sectional views for use in illustration of the first to ninth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the first embodiment shown in FIG. 1 ;
- FIG. 11is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a second embodiment of the invention.
- FIGS. 12 to 21are cross sectional views for use in illustration of the first to tenth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the second embodiment shown in FIG. 11 ;
- FIG. 22is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a third embodiment of the invention.
- FIG. 23is a cross sectional view showing a first variation of the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodiment
- FIG. 24is a cross sectional view showing a second variation of the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodiment
- FIGS. 25 to 32are cross sectional views showing the first to eighth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodiment shown in FIG. 22 ;
- FIG. 33is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a fourth embodiment of the invention.
- FIGS. 34 to 37are cross sectional views for use in illustration of the first to fourth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment shown in FIG. 33 ;
- FIGS. 38 to 41are cross sectional views for use in illustration of a process of manufacturing a 2-power supply semiconductor device including a plurality of field effect transistor according to a first variation of the fourth embodiment
- FIGS. 42 and 43are cross sectional views for use in illustration of the first and second steps in a process of manufacturing a 2-power supply semiconductor device including a plurality of field effect transistors according to a second variation of the fourth embodiment;
- FIG. 44is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a third variation of the fourth embodiment
- FIGS. 45 and 46are cross sectional views for use in illustration of the first and second steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the third variation of the fourth embodiment shown in FIG. 44 ;
- FIG. 47is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a fifth embodiment of the invention.
- FIG. 48is a cross sectional view for use in illustration of the first step in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fifth embodiment shown in FIG. 47 ;
- FIG. 49is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a sixth embodiment of the invention.
- FIGS. 50 to 55are cross sectional views for use in illustration of the first to sixth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the sixth embodiment shown in FIG. 49 ;
- FIG. 56is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a seventh embodiment of the invention.
- FIGS. 57 to 60are cross sectional views for use in illustration of the first to fourth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the seventh embodiment shown in FIG. 56 ;
- FIG. 61is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a first variation of the seventh embodiment
- FIG. 62is a view schematically showing how an isotropic etching agent runs along grain boundaries inside a doped polysilicon film 32 to reach a second gate insulating film 4 , when doped polysilicon film 32 shown in FIG. 56 is isotropically etched;
- FIG. 63is a view schematically showing that an isotropic etching agent does not reach a second gate insulating film 4 because of the absence of grain boundaries in a silicon film 34 , when a silicon film 34 having an amorphous structure as shown in FIG. 61 has its surface isotropically etched in the process of manufacture;
- FIG. 64is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a second variation of the seventh embodiment
- FIGS. 65 to 70are cross sectional views for use in illustration of the first to sixth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the second variation of the seventh embodiment shown in FIG. 64 ;
- FIG. 71is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to an eighth embodiment of the invention.
- FIG. 72is a cross sectional view for use in illustration of the first step in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the eighth embodiment shown in FIG. 71 ;
- FIG. 73is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a ninth embodiment of the invention.
- FIGS. 74 to 78are cross sectional views for use in illustration of the first to fifth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the ninth embodiment shown in FIG. 73 ;
- FIG. 79is a cross sectional view showing a conventional 2-power supply semiconductor device including a plurality of field effect transistors
- FIGS. 80 to 86are cross sectional views for use in illustration of the first to seventh steps in the process of manufacturing the conventional 2-power supply semiconductor device including the plurality of field effect transistors shown in FIG. 79 ;
- FIGS. 87 to 93are cross sectional views for use in illustration of the first to seventh steps in the process of manufacturing another conventional 2-power supply semiconductor device including a plurality of field effect transistors;
- FIG. 94is an enlarged view of region 100 in FIG. 90 .
- a 2-power supply semiconductor deviceincluding a plurality of field transistors according to a first embodiment of the invention, there are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- low Vdd regionthere are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 , and a pair of low concentration, impurity diffusion regions 8 adjacent thereto, spaced apart from each other and having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity region 8constitute an LDD structure.
- a first gate insulating film 6is formed on the first channel region.
- a first gate electrode 18is formed on first insulating film 6 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 , low concentration impurity diffusion regions 8 adjacent thereto, first gate insulating film 6 , and first gate electrode 18form the first field effect transistor.
- Low concentration, n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the second channel region.
- a second gate electrode 19is formed on the second gate insulating film.
- a sidewall nitride film 21 formed of a silicon nitride film which serves as an oxidation protection film to prevent second gate electrode 19 from being oxidizedis formed on a side of second gate electrode 19 .
- a sidewall oxide film 20is formed on a side of sidewall nitride film 21 .
- Second source/drain regions 17 , low concentration impurity diffusion regions 16 adjacent thereto, second gate insulating film 4 and second gate electrode 19form the second field effect transistor.
- the thickness of gate insulating film 4 of the second field effect transistor supplied with high Vddshould be larger than the thickness of the gate insulating film 6 of the first field effect transistor supplied with low Vdd.
- sidewall nitride film 21 serving as an oxidation protection film to prevent second gate electrode 19 from being oxidizedis formed on a side of second gate electrode 19 , and therefore an oxidizing step to form first gate insulating film 6 in the first field effect transistor can be performed with sidewall nitride film 21 present on the side of second gate electrode 19 .
- an oxidizing step to form first gate insulating film 6 in the first field effect transistorcan be performed with sidewall nitride film 21 present on the side of second gate electrode 19 .
- a lower part of a side of the second gate electrode 19can be prevented from being oxidized, and a gate bird's beak can be avoided.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the sidewallis formed of a silicon nitride film, which has a higher ability of preventing diffusion of oxygen atoms than a silicon oxide film, can more surely prevent second gate electrode 19 from being oxidized.
- isolation oxide film 2is formed on the main surface of p type semiconductor substrate 1 to surround an active region.
- Second gate insulating film 4is formed on the active region of the main surface of p type semiconductor substrate 1 .
- a first doped polysilicon film 3is formed on second gate insulating film 4 and on isolation oxide film 2 .
- a resist pattern 5 ais formed on a region of first doped polysilicon film 3 positioned in the high Vdd region to be second gate electrode 19 (see FIG. 1 ).
- first doped polysilicon film 3is anisotropically etched away to form second gate electrode 19 as shown in FIG. 3 , followed by removal of resist pattern 5 a (see FIG. 2 ).
- a silicon nitride film 11is formed on second gate insulating film 4 , second gate electrode 19 and isolation oxide film 2 .
- Silicon nitride film 11is anisotropically etched to form, on a side of second gate electrode 19 , sidewall nitride film 21 formed of a silicon nitride film which serves as an oxidation protection film to prevent second gate electrode 19 from being oxidized.
- a resist pattern 5 bis formed on second gate insulating film 4 , second gate electrode 19 and sidewall nitride film 21 to cover the high Vdd region.
- resist pattern 5 bis formed after second gate electrode 19 is formed on second gate insulating film 4 , resist pattern 5 b is not directly formed on the region—of the surface of second gate insulating film 4 in which second gate electrode 19 is positioned.
- resist pattern 5 bis not directly formed on the region—of the surface of second gate insulating film 4 in which second gate electrode 19 is positioned.
- a resist removing processing or a light etching processingcan be prevented.
- defectsmay be prevented from being generated in the region of the surface of second gate insulating film 4 .
- the condition of the anisotropic etching to silicon nitride film 11may be adjusted so that sidewall nitride film 21 serving as the oxidation protection film has an arbitrary thickness.
- second source/drain regions 17 and low concentration impurity diffusion regions 16in the manufacturing process which will be described, the distance between the source region and the drain region (the length of the channel region) can be adjusted, and second source/drain regions 17 and low concentration impurity diffusion regions 16 having an offset structure can be readily formed.
- a high electric field in the vicinity of the boundary region between the channel region, second source/drain regions 17 and low concentration impurity diffusion regions 16can be reduced.
- the generation of electrons with high energycan be prevented.
- second gate insulating film 4 present in the low Vdd regionis removed by means of isotropic etching, and the structure as shown in FIG. 5 results. Thereafter, resist pattern 5 b is removed.
- First gate insulating film 6is formed on the portion of the main surface of p type semiconductor substrate 1 positioned in the low Vdd region, on the surface of second gate insulating film 4 , and on second gate electrode 19 by means of thermal oxidation.
- the thermal oxidation to form first gate insulating film 6can be performed after sidewall nitride film 21 serving as the oxidation protection film is formed on the side of second gate electrode 19 .
- a lower part of the side of second gate electrode 19can be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- a second doped polysilicon film 7is formed to generally cover the entire surface.
- a resist pattern 5 cis formed on the region of second doped polysilicon film 7 to be the first gate electrode 18 (see FIG. 1 ). As a result, the structure as shown in FIG. 7 results.
- first gate electrode 18a part of second doped polysilicon film 7 is anisotropically etched away to form first gate electrode 18 (see FIG. 1 ).
- silicon oxide film 6 formed by the thermal oxidation during forming first gate insulating film 6is on second gate electrode 19 .
- silicon oxide film 6serves as a stopper, so that damages such as partial removal of second gate electrode 19 by the anisotropic etching can be prevented.
- second doped polysilicon film 7is formed on first gate insulating film 6 , resist pattern 5 d (see FIG.
- first gate insulating film 64is not directly formed on first gate insulating film 64 positioned under first gate electrode in the manufacturing process according to the first embodiment. Therefore, as is the case with second gate insulating film 4 , defects caused by a processing of removing a resist pattern on the surface of first gate insulating film 6 can be prevented. Thereafter, resist pattern 5 c (see FIG. 7 ) is removed. A resist pattern 5 d (see FIG. 8 ) is formed to cover the low Vdd region. Thus, the structure as shown in FIG. 8 results. At the time, second doped polysilicon film 7 also remains on a side of sidewall nitride film 21 .
- Second doped polysilicon film 7 on the side of sidewall nitride film 21is removed by means of isotropic etching. Thereafter, resist pattern 5 d is removed.
- An n type impurityis introduced into a prescribed region of the main surface of p type semiconductor substrate 1 to form low concentration, n type impurity diffusion regions 8 and 16 as shown in FIG. 9 .
- the n type impuritymay be phosphorous or arsenic.
- Sidewall oxide films 9 and 20are formed on sides of first gate electrode 18 and sidewall nitride film 21 .
- First and second gate insulating films 4 and 6 in the region other than those positioned under first and second gate electrodes 18 and 19 , sidewall oxide films 9 and 20 and sidewall nitride film 21are etched away.
- An n type impurityis introduced into a prescribed region of the main surface of p type semiconductor substrate 1 to form high concentration, n type impurity diffusion regions 10 and 17 as shown in FIG. 10 .
- the 2-power supply semiconductor device according to the first embodimentis thus manufactured.
- sidewall nitride film 21 serving as the oxidation protection filmis formed on a side of second gate electrode 19 , the same effects can be brought about by forming sidewall nitride film 21 serving as the oxidation protection film on a side of first gate electrode 18 .
- a 2-power supply semiconductor deviceincluding a plurality of field transistors according to a second embodiment of the invention
- a first field effect transistorsupplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- first source/drain regions 10 and impurity diffusion regions 26there are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 and a pair of impurity diffusion regions 26 , spaced apart from each other and having a first channel region therebetween. Intermediate concentration, n type impurity diffusion region 26 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity region 26 constitute an LDD structure.
- a first gate insulating film 6is formed on the first channel region.
- a first gate electrode 18is formed on first insulating film 6 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 , impurity diffusion regions 26 , first gate insulating film 6 , and first gate electrode 18form the first field effect transistor.
- a pair of second source/drain regions 17there are formed, on the main surface of semiconductor substrate 1 , a pair of second source/drain regions 17 , pairs of impurity diffusion regions 16 and 12 adjacent thereto, spaced apart from each other and having a second channel therebetween.
- Low concentration, n type impurity diffusion region 16 formed adjacent to the second channel region, intermediate concentration, n type impurity diffusion region 12 and high concentration, n type impurity-diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the second channel region.
- a second gate electrode 19is formed on second gate insulating film 4 .
- a sidewall nitride film 21 serving as an oxidation protection film to prevent second gate electrode 19 from being oxidizedis formed on a side of second gate electrode 19 .
- a sidewall oxide film 20is formed on a side of sidewall nitride film 21 .
- Second source/drain regions 17 , impurity diffusion regions 16 and 12 , second gate insulating film 4 , and second gate electrode 19form the second field effect transistor.
- the thickness of the second gate insulating film 4 of the second field effect transistor supplied with high Vddshould be larger than the thickness of the first gate insulating film 6 of the first field effect transistor supplied with low Vdd.
- the second source/drain regions 17 and impurity diffusion regions 12 and 16 of the second field effect transistors which are supplied with high Vddhave a three-region LDD structure, a high electric field in the boundary region between the second channel region and second source/drain regions as well as impurity diffusion regions 12 and 16 can be more effectively reduced. As a result, the fluctuation of the threshold voltage of the second field effect transistor can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- isolation oxide film 2 to surround an active regionis formed on the main surface of p type semiconductor substrate 1 .
- Second gate insulating film 4is formed on the active region of the main surface of semiconductor substrate 1 .
- a first doped polyslicon film 3is formed on second gate insulating film 4 and isolation oxide film 2 .
- a resist pattern 5 ais formed on the region of first doped polysilicon film 3 positioned in the high Vdd region to be second gate electrode 19 (see FIG. 11 ).
- n type impurityis introduced into a prescribed region of semiconductor substrate 1 to form a low concentration, n type impurity diffusion region 16 as shown in FIG. 13 .
- the n type impurity usedis phosphorus, the introduction energy is 20 keV, and the dose is 2 ⁇ 10 13 cm ⁇ 2 .
- the introduction energymay be in the range from 10 to 30 keV.
- second gate electrode 19has been formed on second gate insulating film 4 , a resist pattern is not directly formed in the region of the surface of second gate insulating film 4 in which second gate electrode 19 is positioned, in the process of manufacturing which will be described. Defects in the region of the surface of second gate insulating film 4 which are caused by a processing of removing the resist patterns or a light etching processing can be prevented. Resist pattern 5 b is thereafter removed.
- a silicon nitride film 11is formed on second gate insulating film 4 , second gate electrode 19 and isolation oxide film 2 .
- the structure as shown in FIG. 14results.
- Silicon nitride film 11is then anisotropically etched to form sidewall nitride film 21 (see FIG. 11 ) which serves as an oxidation protection film to prevent second gate electrode 19 from being oxidized on a sidewall of second gate electrode 19 .
- Resist pattern 5 cis formed on second gate insulating film 4 , second gate electrode 19 and sidewall nitride film 21 to cover the high Vdd region to obtain the structure as shown in FIG. 15 .
- second gate insulating film 4 present in the low Vdd regionis isotropically etched to obtain the structure as shown in FIG. 16 .
- Resist pattern 5 cis then removed away.
- First gate insulating film 6is formed by means of thermal oxidation on the portion of the main surface of semiconductor substrate 1 positioned in the low Vdd region, on the surface of second gate insulating film 4 , and on second gate electrode 19 .
- the structure as shown in FIG. 17thus results.
- the thermal oxidation to form first gate insulating film 6may be performed after forming sidewall nitride film 21 serving as the oxidation protection film to prevent second gate electrode 19 from being oxidized on a side of second gate electrode 19 .
- sidewall nitride film 21serving as the oxidation protection film to prevent second gate electrode 19 from being oxidized on a side of second gate electrode 19 .
- a second doped polysilicon film 7(see FIG. 18 ) is formed to generally cover the entire surface.
- a resist pattern 5 d(see FIG. 18 ) is formed on the region of second doped polysilicon film 7 to be the first gate electrode (see FIG. 11 ).
- the structure as shown in FIG. 18results.
- first gate electrode 18a part of second doped polysilicon film 7 is anisotropically etched away to form first gate electrode 18 (see FIG. 11 ).
- silicon oxide film 6 formed by the thermal oxidation during forming first gate insulating film 6is present on second gate electrode 19 . Therefore, during the anisotropic etching for forming first gate electrode 18 , silicon oxide film 6 serves as a stopper, so that damages such as partial removal of second gate electrode 19 by the anisotropic etching can be prevented.
- resist pattern 5 dsee FIG. 18
- a resist pattern 5 eis formed to generally cover the low Vdd region.
- second doped polysilicon film 7also remains on a side of sidewall nitride film 21 .
- n type impurityis introduced into a prescribed region of the main surface of semiconductor substrate 1 , and thus intermediate concentration, n type impurity diffusion regions 26 and 12 are formed as shown in FIG. 20 .
- the n type impurityis arsenic, the introduction energy is 60 keV, and the dose is 2 ⁇ 10 13 cm ⁇ 2 .
- the introduction energymay be in the range from 30 to 80 keV.
- n type impurityis introduced into a prescribed region of the main surface of semiconductor substrate. As shown in FIG. 21 , high concentration, n type impurity diffusion regions 10 and 17 are formed.
- the n type impurityis arsenic
- the introduction energyis 40 keV
- the doseis 5 ⁇ 10 13 cm ⁇ 2 .
- the introduction energymay be in the range from 30 to 60 keV.
- the 2-power supply semiconductor device including the plurality of field effect transistors according to the second embodimentis manufactured.
- a 2-power supply semiconductor deviceincluding a plurality of field transistors according to a third embodiment of the invention, there are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- low Vdd regionthere are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 , and a pair of impurity diffusion regions 8 , spaced apart from each other and having a first channel region.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity region 8constitute an LDD structure.
- An oxide nitride film 13 serving as a gate insulating filmis formed on the first channel region.
- a first gate electrode 18is formed on oxide nitride film 13 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 and impurity diffusion regions 8 , oxide nitride film 13 , and first gate electrode 18form the first field effect transistor.
- n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the channel region.
- a second gate electrode 19is formed on second gate insulating film 4 .
- An oxide nitride film 13is formed on a side of second gate electrode 19 and on second gate insulating film 4 .
- a sidewall oxide film 20is formed on oxide nitride film 13 .
- Second source/drain regions 17 , and impurity diffusion regions 16 , second gate insulating film 4 , and second gate electrode 19form the second field effect transistor.
- the gate insulating film 13 of the first field effect transistoris formed of an oxide nitride film, an end of second gate electrode 19 in the junction of a lower part of the side of second gate electrode 19 and second gate insulating film 4 can be prevented from being excessively oxidized.
- the generation of a gate bird's beakcan be restricted.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the first gate insulating filmis formed of oxide nitride film 13 , the driving capability of the transistor may be improved in terms of thickness as compared to a conventional silicon oxide film or the like.
- a first variation of the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodimenthas basically the same structure as the 2-power supply semiconductor device according to the first embodiment shown in FIG. 1 .
- the first gate insulating film 13is formed of oxide nitride film.
- a second variation of the third embodiment shown in FIG. 24has basically the same structure as the device according to the second embodiment shown in FIG. 11 .
- the first gate insulating film 13is formed of oxide nitride film. Therefore, the driving capability of the transistor may be improved as compared to the case of using the conventional silicon oxide film in terms of thickness in addition to the effects brought about according to the first and second embodiments.
- FIGS. 25 to 32a process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors shown in FIG. 22 according to the third embodiment will be described.
- the manufacturing process shown in FIG. 25is identical to the manufacturing process according to the first embodiment shown in FIG. 2 .
- first doped polysilicon film 3is anisotropically etched away, using a resist pattern 5 a (see FIG. 25 ) as a mask, to form second gate electrode 19 (see FIG. 22 ), followed by removal of resist pattern 5 a (see FIG. 25 ).
- a resist pattern 5 b(see FIG. 26 ) is formed on second gate insulating film 4 and on second gate electrode 19 to cover the high Vdd region, and the structure as shown in FIG. 26 results.
- resist pattern 5 bis formed after second gate electrode 19 is formed on second gate insulating film 4 , resist pattern 5 b is not directly formed in the region of the surface of second gate insulating film 4 in which second gate electrode 19 is positioned.
- defects in the region of the surface of second insulating film 4 caused by a processing of removing resist pattern 5 b or a light etching processingcan be prevented.
- Second gate insulating film 4 present in the low Vdd regionis isotropically etched away to obtain the structure as shown in FIG. 27 . Thereafter, resist pattern 5 b is removed.
- oxide nitride film 13 to be the first gate insulating filmis formed at the position of the main surface of semiconductor substrate 1 positioned in the low Vdd region, on the surface of second gate insulating film 4 , and on second gate electrode 19 by means of thermal oxidation using N 2 O or O 2 as a gas atmosphere.
- oxide nitride film 13is formed as the first gate insulating film, an end of second gate electrode 19 can be prevented from being excessively oxidized in the junction of a lower part of the side of second gate electrode 19 and second gate insulating film 4 .
- a gate bird's beakcan be prevented.
- oxide nitride film 13is formed as the first gate insulating film, the thickness of oxide nitride film 13 as the first gate insulating film may be smaller than a conventional silicon oxide film, while maintaining a prescribed breakdown voltage. As a result, the driving voltage of the first field effect transistor can be reduced.
- the manufacturing process as shown in FIGS. 29 to 32is substantially identical to the manufacturing process according to the first embodiment shown in FIGS. 7 to 10 .
- the 2-power supply semiconductor device according to the third embodiment as shown in FIG. 22is manufactured.
- a 2-power supply semiconductor device including a plurality of field transistorsthere are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second power supply voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- first source/drain regions 10there are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 , and a pair of impurity diffusion regions 8 , spaced apart from each other and having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity region 8constitute an LDD structure.
- a first gate insulating film 6is formed on the first channel region.
- a first gate electrode 18is formed on first insulating film 6 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 , impurity regions 8 , first gate insulating film 6 , and first gate electrode 18form the first field effect transistor.
- a pair of second source/drain regions 17 and a pair of impurity diffusion regions 16spaced apart from each other and having a second channel therebetween.
- Low concentration, n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the second channel region.
- a nitrogen doped polysilicon film 14 serving as an anti-oxidation conductive filmis formed on second gate insulating film 4 .
- a first doped polysilicon film 13 doped with a p type or n type impurityis formed on nitrogen doped polysilicon film 14 .
- Nitrogen doped polysilicon film 14 and first doped polysilicon film 3form a second gate electrode 19 .
- a sidewall oxide film 20is form on a side of second gate electrode 19 .
- Second source/drain regions 17 , impurity diffusion regions 16 , second gate insulating film 4 , and second gate electrode 19form the second field effect transistor.
- the thickness of second gate insulating film 4 of the second field effect transistorshould be larger than the thickness of the first gate insulating film 6 of the first field effect transistor in view of breakdown voltage.
- first gate insulating film 6is formed using nitrogen doped polysilicon film 14 as a mask, an oxidizing step may be performed while hardly oxidizing the surface of nitrogen doped polysilicon film 14 .
- an oxidizing stepmay be performed while hardly oxidizing the surface of nitrogen doped polysilicon film 14 .
- a lower part of a side of second gate electrode 19is not oxidized, and a gate bird's beak can be prevented.
- the threshold voltage of the second field effect transistorcan be prevented from increasing, and electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- first and second gate insulating films 6 and 4are formed in the above-described manner, a conductive layer may be later formed in the region positioned above first and second gate insulating films 4 and 6 , and therefore first and second gate electrodes 18 and 19 may be formed in a single patterning processing. As a result, the number of steps included in the manufacture of the semiconductor device may be reduced.
- nitrogen doped polysilicon film 14is formed on second gate insulating film 4 , a resist pattern is not directly formed on second gate insulating film 4 .
- defectssuch as local irregularities in the gate insulating film as formed during removing a resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating.
- Isolation oxide film 2is formed to surround an active region on the main surface of p type semiconductor substrate 1 .
- Second gate insulating film 4is formed on the active region of the main surface of semiconductor substrate 1 .
- Nitrogen doped polysilicon film 14 to be the anti-oxidation conductive filmis formed on second gate insulating film 4 and isolation oxide film 2 .
- Resist pattern 5 ais formed on nitrogen doped polysilicon film 14 positioned in the high Vdd region. Thus the structure as shown in FIG. 34 is obtained. Since nitrogen doped polysilicon film 14 is formed on second gate insulating film 4 and resist pattern 5 a is formed, resist pattern 5 a is not directly formed on the surface of second gate insulating film.
- Nitrogen doped polysilicon film 14 and second gate insulating film 4 present in the low Vdd regionare removed by means of isotropic etching, and the structure as shown in FIG. 35 results. Resist pattern 5 a is thereafter removed.
- first gate insulating film 6is formed on the main surface of semiconductor substrate 1 positioned in the low Vdd region. At the time, the surface of nitrogen doped polysilicon film 14 is little oxidized, because its surface had nitrogen introduced.
- First doped polysilicon film 3is formed on first gate insulating film 6 , nitrogen doped polysilicon film 14 and isolation oxide film 2 .
- Resist patterns 5 b and 5 care formed on the regions of first doped polysilicon film 3 to be first and second gate electrodes 18 and 19 (see FIG. 33 ), and the structure as shown in FIG. 37 results.
- first and second gate electrodes 18 and 19are anisotropically etched away to form first and second gate electrodes 18 and 19 (see FIG. 33 ). Since nitrogen doped polysilicon film 14 serving as the anti-oxidation conductive film is formed on second gate insulating film 4 , first and second gate electrodes 18 and 19 may be formed in a single etching processing after first and second gate insulating films 6 and 4 are formed. In addition, since first gate electrode 18 and second gate electrode 19 may be formed in a single anisotropic etching processing, the number of steps included in the manufacture of the semiconductor device may be reduced.
- nitrogen doped polysilicon film 14is formed on second gate insulating film 4 , nitrogen doped polysilicon film 14 serves as a barrier against an impurity when the impurity is introduced to form second source/drain regions 17 and impurity diffusion regions 16 (see FIG. 33 ). As a result, the impurity can be effectively prevented from being introduced into the second channel region. As a result, erroneous operations of the second field effect transistor caused by introduction of the impurity into the second channel region can be more effectively prevented.
- the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodimentis thus manufactured.
- Isolation oxide film 2is formed on the main surface of p type semiconductor substrate 1 to surround an active region.
- An oxide film(not shown) is formed on the main surface of semiconductor substrate 1 .
- a resist pattern(not shown) is formed on the oxide film positioned in the low Vdd region. Using the resist pattern as a mask, an impurity is introduced into the main surface of semiconductor substrate 1 positioned in the high Vdd region. Using the resist pattern as a mask, the oxide film positioned in the high Vdd region is isotropically etched away. Thereafter, the resist pattern is removed to form the structure as shown in FIG. 38 .
- the manufacturing steps shown in FIGS. 39 and 40are substantially identical to the steps of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment.
- an oxide film 28 serving as a substrate protection filmis formed on the main surface of semiconductor substrate positioned in the low Vdd region as shown in FIG. 39 .
- the main surface of semiconductor substrate 1 positioned in the low Vdd regionis not directly oxidized. Since oxide film 4 and nitrogen doped polysilicon film 14 are formed on oxide film 28 , during isotropically etching away nitrogen doped polysilicon film 14 from the low Vdd region as shown in FIG.
- oxide film 28 having a sufficient thicknesscan prevent the main surface of semiconductor substrate 1 positioned in the low Vdd region from being directly damaged by the isotropic etching.
- first gate insulating film 6see FIG. 33
- the fluctuation of the threshold voltage of the first field effect transistorcan be prevented.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the manufacturing process according to the first variation of the fourth embodiment shown in FIG. 41is substantially identical to the manufacturing process according to the fourth embodiment shown in FIG. 37 .
- An impurityis thereafter introduced into a prescribed region of the main surface of semiconductor substrate 1 , followed by formation of sidewall oxide films 9 and 20 (see FIG. 33 ) on sides of first and second gate electrodes 18 and 19 (see FIG. 33 ), to form the semiconductor device as shown in FIG. 33 .
- resist pattern 5 a(see FIG. 35 ) is removed. Then, the entire surface of semiconductor substrate 1 is oxidized to form an oxide film 29 on the main surface of semiconductor substrate 1 positioned in the low Vdd region to obtain the structure as shown in FIG. 42 .
- oxide film 29(see FIG. 42 ) is isotropically etched away.
- oxide film 29(see FIG. 42 ) is thus isotropically etched away, possible damages generated by etching on the main surface positioned in the low Vdd region of semiconductor substrate 1 caused by an etching processing to remove oxide film 4 (see FIG. 34 ) and nitrogen doped polysilicon film 14 (see FIG. 34 ) from the main surface of semiconductor substrate 1 positioned in the low Vdd region can be removed by isotropically etching a part of the main surface of semiconductor substrate 1 with the defects.
- first gate insulating film 6As a result, during forming first gate insulating film 6 (see FIG. 33 ), the deterioration of the quality of first gate insulating film 6 because of damages by etching such as local irregularities on the surface of semiconductor substrate 1 may be prevented. As a result, the fluctuation of the threshold voltages of the field effect transistors may be prevented, and as a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- the steps to manufacture the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment shown in FIGS. 36 and 37are performed to obtain the semiconductor device as shown in FIG. 33 .
- a 2-power supply semiconductor device including a plurality of field effect transistors according to a third variation of the fourth embodiment of the inventionhas substantially the same structure as the 2-power supply semiconductor device according to the fourth embodiment shown in FIG. 33 .
- a doped polysilicon film 32 having a conductive impurity between second gate insulating film 4 and nitrogen doped polysilicon film 14is formed in the device according to the third variation.
- the formation of a depletion layer caused by a reduction in the density of the conductive impurity in the vicinity of second gate insulating film 4 when a voltage is supplied to gate electrode 19can be restrained.
- the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layercan be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- isolation oxide film 2is formed to surround an active region on the main surface of p type semiconductor substrate 1 .
- Second gate insulating film 4is formed on the active region of the main surface of semiconductor substrate 1 .
- Doped polysilicon film 32 having a conductive impurityis formed between second gate insulating film 4 and isolation oxide film 2 .
- Nitrogen doped polysilicon film 14is formed on doped polysilicon film 32 .
- a polysilicon film 7is formed to generally cover the entire semiconductor device as shown in FIG. 46 .
- Resist patterns 5 g and 5 hare formed on polysilicon film 7 .
- resist patterns 5 g and 5 has masks, an anisotropic etching is performed to partially remove doped polysilicon film 7 , nitrogen doped polysilicon film 14 and doped polysilicon film 32 to form first and second gate electrodes 18 and 19 (see FIG. 44 ).
- nitrogen doped polysilicon film 14is formed in the high Vdd region, the same effects can be brought about by forming nitrogen doped polysilicon film 14 in the low Vdd region.
- a 2-power supply semiconductor deviceincluding a plurality of field transistors according to a fifth embodiment of the invention, there are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- first source/drain regions 10there are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 , and a pair of impurity diffusion regions 8 spaced apart from each other and having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity diffusion region 8constitute an LDD structure.
- a first gate insulating film 6is formed on the first channel region.
- a first gate electrode 18is formed on first insulating film 6 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 , impurity diffusions 8 , first gate insulating film 6 , and first gate electrode 18form the first field effect transistor.
- the high Vdd regionthere are formed, on the main surface of semiconductor substrate 1 , a pair of second source/drain regions 17 , and a pair of impurity diffusion regions 16 , spaced apart from each other and having a second channel therebetween.
- Low concentration, n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- Second gate insulating film 4is formed on the second channel region.
- Doped polysilicon film 32 having a conductive impurityis formed on second gate insulating film 4 .
- a nitride film 27is formed on a doped polysilicon film 32 .
- a doped polysilicon film 7is formed on nitride film 27 .
- Doped polysilicon film 32 , nitride film 27 and doped polysilicon film 7form a second gate electrode 19 .
- a sidewall oxide film 9is formed on a side of second gate electrode 19 .
- nitride film 27is formed by nitriding the surface of doped polysilicon film 32 by lamp annealing as in the manufacturing steps which will be described and is a tunnel insulating film through which a current may be passed when voltage is supplied to gate electrode 19 .
- Second source/drain regions 17 , impurity diffusion regions 16 , second gate insulating film 4 , and second gate electrode 19form the second field effect transistor.
- doped polysilicon film 32 and nitride film 27are formed on second gate insulating film 4 , it is not necessary to form a resist pattern directly on the surface of second gate insulating film 4 .
- An oxidizing step to form first gate insulating film 6may be performed, using nitride film 27 as a mask before forming second gate electrode 19 .
- a lower part of a side of second gate electrode 19is not oxidized in the step of oxidizing first gate insulating film 6 , and therefore a gate bird's beak can be prevented. Therefore, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- doped polysilicon film 32is formed on second gate insulating film 4 , a resist pattern is not formed directly on second gate insulating film 4 . Therefore, as a result, defects such as local irregularities in the gate insulating film as formed during removing the resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating.
- first and second gate electrodes 18 and 19may be formed in a single patterning processing by forming a conductive layer on the regions positioned on first and second gate insulating films 4 and 6 . As a result, the number of steps included in the manufacture of semiconductor device may be reduced.
- doped polysilicon film 32 including a conductive impurityis formed on second gate insulating film 4 , when a voltage is supplied to gate electrode 19 , the formation of a depletion layer caused by a reduction in the density of the conductive impurity in the vicinity of second gate insulating film 4 may be restricted. As a result, the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layer can be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- isolation oxide film 2is formed to surround an active region on the main surface of p type semiconductor substrate 1 .
- Second gate insulating film 4is formed on the active region on the main surface of semiconductor substrate 1 .
- Doped polysilicon film 32 including a conductive impurityis formed on second gate insulating film 4 and isolation oxide film 2 .
- the surface of doped polysilicon film 32is nitrided by means of lamp annealing to form nitride film 27 .
- doped polysilicon film 32 and nitride film 27are formed on second gate insulating film 4 , a resist pattern does not have to be formed directly on the surface of second gate insulating film 4 .
- an oxidizing step to form first gate insulating film 6 using nitride film 27 as a maskmay be performed before forming second gate electrode 19 .
- a lower part of a side of second gate electrode 19is not oxidized, and as a result, a gate bird's beak can be prevented.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- first and second gate insulating films 6 and 4may be formed in the above-described manner, in the step corresponding to the step shown in FIG. 37 , doped polysilicon film 7 (see FIG. 47 ) may be formed in the region positioned above first and second gate insulating films 6 and 4 , and first and second gate electrodes 18 and 19 may be formed in a single patterning processing. As a result, the number of steps included in the manufacture of the semiconductor device may be reduced.
- a 2-power supply semiconductor device including a plurality of field transistorsthere are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- first source/drain regions 10there are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 , and a pair of impurity diffusion regions 8 spaced apart from each other and having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity diffusion region 8constitute an LDD structure.
- a first gate insulating film 6is formed on the first channel region.
- a first gate electrode 18is formed on first gate insulating film 6 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 , impurity diffusion regions 8 , first gate insulating film 6 , and first gate electrode 18form the first field effect transistor.
- a pair of second source/drain regions 17there are formed, on the main surface of semiconductor substrate 1 , a pair of second source/drain regions 17 , a pair of impurity diffusion regions 16 spaced apart from each other and having a second channel therebetween.
- Low concentration, n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the second channel region.
- a first doped polysilicon film 3is formed on second gate insulating film 4 .
- An insulating film 6 of the same material as that of first gate insulating film 6is formed on first doped polysilicon film 3 .
- a second doped polysilicon film 22is formed on insulating film 6 .
- First doped polysilicon film 3 , insulating film 6 , and second doped polysilicon film 22form second gate electrode 19 .
- a sidewall oxide film 20is formed on a side of second gate electrode 19 .
- Second source/drain regions 17 , impurity diffusion regions 16 , second gate insulating film 4 , and second gate electrode 19form the second field effect transistor.
- second gate electrode 19is formed to have first doped polysilicon 3 , insulating film 6 in the high Vdd region and second doped polysilicon film 22 , a resist pattern is not directly formed on the surface of second gate insulating film 4 in the step of manufacture which will be described, an oxidizing step to form first gate insulating film 6 in the low Vdd region may be performed before forming second electrode 19 .
- an oxidizing step to form first gate insulating film 6 in the low Vdd regionmay be performed before forming second electrode 19 .
- a gate bird's beak caused by oxidation of a side of second electrode 19can be prevented.
- a voltage imposed on second gate insulating film 4can be reduced by a voltage drop at insulating film 6 in the high Vdd region.
- the thickness of first gate insulating film 6 in low Vdd regionis t 1
- the thickness of second gate insulating film 4 t 2the thickness of insulating film 6 in the high Vdd region t 3 , a voltage supplied to first gate electrode 18 V 1 , and a voltage supplied to second gate electrode 19 V 2
- the thicknesses of insulating film 6 in the high Vdd region, first gate insulating film 6 in the low Vdd region and second gate insulating film 4may be adjusted such that t 1 /(t 2 +t 3 ) is substantially equal to V 1 /V 2 , and the static characteristic of first and second field effect transistors can be adjusted to be substantially equal to each other.
- isolation oxide film 2is formed on the main surface of p type semiconductor substrate 1 to surround an active region.
- Second gate insulating film 4is formed on the active region of the main surface of semiconductor substrate 1 .
- First doped polysilicon film 3is formed on second gate insulating film 4 and isolation oxide film 2 .
- a resist pattern 5 ais formed on first doped polysilicon film 3 positioned in the high Vdd region.
- First doped polysilicon film 3 and second gate insulating film 4 present in the low Vdd regionare removed by isotropic etching. Thereafter, resist pattern 5 a is removed. Thus, the structure as shown in FIG. 51 results.
- First gate insulating film 6is formed on the portion of the main surface of semiconductor substrate 1 positioned in the low Vdd region and on first doped polysilicon film 3 by means of thermal oxidation.
- the structure as shown in FIG. 52results.
- an oxidizing step to form first gate insulating film 6is performed, a gate bird's beak caused by oxidation of a side of second gate electrode 19 can be prevented.
- first doped polysilicon film 3is formed on second gate insulating film 4 , a resist pattern is not directly formed onto the surface of second gate insulating film 4 .
- a processing of removing the resist patternis not directly performed on the surface of second gate insulating film 4 , and defects on the surface of second gate insulating film 4 can be prevented.
- second doped polysilicon film 7is formed on first gate insulating film 6 and isolation oxide film 2 .
- resist patterns 5 b and 5 care formed on the portion of second doped polysilicon film 7 in the low Vdd region and on the region to be second gate electrode 19 (see FIG. 49 ).
- resist patterns 5 b and 5 cas masks, anisotropic etching is performed to remove part of second doped polysilicon film 7 , first gate insulating film 6 , and first doped polysilicon 3 to form second gate electrode 19 (see FIG. 49 ). Thereafter, resist patterns 5 b and 5 c (see FIG. 53 ) are removed. Resist patterns 5 d and 5 e are formed on second insulating film 4 , second gate electrode 19 , and the region to be the gate electrode 18 of doped polysilicon film 7 (see FIG. 49 ). Thus, the structure as shown in FIG. 54 results.
- first gate electrode 18(see FIG. 49 ) is formed.
- resist patterns 5 d and 5 eare removed to obtain the structure as shown in FIG. 55 .
- an impurityis introduced into a prescribed region of the main surface of semiconductor substrate 1 , followed by formation of sidewall oxide films 9 and 20 (see FIG. 49 ) on sides of first and second gate electrodes 18 and 19 , to form the semiconductor device as shown in FIG. 49 .
- a 2-power supply semiconductor device including a plurality of field transistorsthere are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- a pair of first source/drain regions 10 and a pair of impurity diffusion regions 8spaced apart from each other and having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity region 8constitute an LDD structure.
- a first gate insulating film 6is formed on the first channel region.
- a doped polysilicon film 31is formed on first gate insulating film 6 .
- Doped polysilicon film 31has a relatively small thickness for example of about 500 ⁇ .
- a natural oxide film 30is formed on doped polysilicon film 31 .
- a doped polysilicon film 7is formed on natural oxide film 30 .
- Doped polysilicon film 31 , natural oxide film 30 and doped polysilicon film 7form first gate electrode 18 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 and impurity diffusion regions 8 , first gate insulating film 6 and first gate electrode 18form first field effect transistor.
- n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the second channel region.
- a doped polysilicon film 32is formed on second gate insulating film 4 .
- Doped polysilicon film 32has a relatively small thickness for example of about 500 ⁇ .
- Natural oxide film 30is formed on doped polysilicon film 32 .
- Doped polysilicon film 7is formed on natural oxide film 30 .
- Doped polysilicon film 32 , natural oxide film 30 and doped polysilicon film 7constitute second gate electrode 19 .
- a sidewall oxide film 9is formed on a side of second gate electrode 19 .
- Second source/drain regions 17 , impurity diffusion regions 16 , second gate insulating film 4 , and second gate electrode 19form the second field effect transistor.
- doped polysilicon films 31 and 32are formed on first and second gate insulating films 6 and 4 , it is not necessary to form a resist pattern directly on the surfaces of first and second gate insulating films 6 and 4 in the following manufacturing steps.
- an oxidizing step to form first gate insulating film 6can be performed using doped polysilicon film 32 as a mask, before forming second gate electrode 19 .
- a lower part of a side of second gate electrode 19can be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the thicknesses of doped polysilicon films 31 and 32 to be etched away for forming first and second gate electrodes 18 and 19can be made substantially equal in the regions to form first and second gate electrodes 18 and 19 .
- the amount of etching to form first gate electrode 18can be almost the same as the amount of etching to form second gate electrode 19 .
- the amount of overetching in forming first and second gate electrodes 18 and 19can be reduced. Therefore, damages caused by overetching of semiconductor substrate 1 positioned under doped polysilicon films 31 and 32 to be etched away can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented.
- doped polysilicon films 31 and 32are formed on first and second gate insulating films 6 and 4 , a resist pattern is not formed directly on first and second gate insulating films 6 and 4 .
- defectssuch as local irregularities in the gate insulating film caused by the step of ashing to remove a resist pattern can be prevented from being generated in first and second gate insulating films 6 and 4 .
- FIGS. 57 to 60a method of manufacturing the 2-power supply semiconductor device according to the seventh embodiment of the invention will be described.
- isolation oxide film 2 to surround an active regionis formed on the main surface of p type semiconductor substrate 1 .
- Second gate insulating film 4is formed on the active region of the main surface of semiconductor substrate 1 .
- Doped polysilicon film 32is formed on second gate insulating film 4 and isolation oxide film 2 . Thereafter, a resist pattern 5 f is then formed on doped polysilicon film 32 positioned in the high Vdd region.
- second gate insulating film 4 and doped polysilicon film 32 positioned in the low Vdd regionare etched away, followed by removal of resist pattern 5 f . Since doped polysilicon film 32 is formed on second gate insulating film 4 , resist pattern 5 f is not directly formed on second gate insulating film 4 . As a result, defects such as fine irregularities in the surface of second gate insulating film 4 caused by the removal of resist pattern 5 f can be prevented.
- first gate insulating film 6is formed on the main surface of semiconductor substrate 1 positioned in the low Vdd region and on doped polysilicon film 32 .
- Doped polysilicon film 31is then formed on first gate insulating film and isolation oxide film 2 .
- a resist pattern 5 iis formed on doped polysilicon film 31 in the low Vdd region.
- an oxidizing step to form first gate insulating film 6can be performed using doped polysilicon film 32 as a mask before forming second gate electrode 19 (see FIG. 56 ).
- a lower part of a side of second gate electrode 19can be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- the amount of etching to form first gate electrode 18can be substantially the same as the amount of etching to form second gate electrode 19 .
- the amount of overetching during forming first and second gate electrodes 18 and 19can be reduced.
- doped polysilicon film 31 and gate insulating film 6 positioned in the high Vdd regionare etched away, using resist pattern 5 i as a mask, followed by removal of resist pattern 5 i .
- resist pattern 5 ias a mask
- resist pattern 5 ias a mask
- a part of the surfaces of first and second doped polysilicon films 31 and 32is isotropically etched away.
- a doped polysilicon film 7 having for example a thickness of about 1500 ⁇is formed on the entire surface of semiconductor substrate 1 .
- natural oxide film 30has been formed on the surfaces of doped polysilicon films 31 and 32 .
- Resist patterns 5 g and 5 hare then formed on doped polysilicon film 7 .
- the structure as shown in FIG. 60results.
- first and second gate electrodes 18 and 19are formed by resist patterns 5 g and 5 h as masks.
- An impurityis introduced into a prescribed region of the main surface of semiconductor substrate 1 , followed by formation of a sidewall oxide film 9 (see FIG. 56 ) on sides of first and second gate electrodes 18 and 19 , and the semiconductor device as shown in FIG. 56 results.
- the thickness of doped polysilicon films 31 and 32is for example not less than 100 ⁇ , during etching to form first and second gate electrodes 18 and 19 , part of doped polysilicon films 31 and 32 having a sufficient thickness will not be removed during removing natural oxide film 30 , and damages by the etching are not caused on first and second gate insulating films 6 and 4 positioned under doped polysilicon films 31 and 32 and in the main surface of semiconductor substrate 1 .
- the etching process to remove natural oxide film 30can be readily performed, and the etching margin can be improved as compared to the case of removing natural oxide film 30 by etching the doped polysilicon films.
- a 2-power supply semiconductor device including a plurality of field effect transistors according to a first variation of the seventh embodimenthas basically the same structure as the 2-power supply semiconductor device according to the seventh embodiment shown in FIG. 56 with difference being that silicon films 33 and 34 having an amorphous structure are formed on first and second gate insulating films 6 and 4 . Since silicon films 33 and 34 formed on first and second gate insulating films 6 and 4 have an amorphous structure, an isotropic etching agent used for isotropically etching silicon films 33 and 34 does not run inside silicon films 33 and 34 to reach first and second gate insulating films 6 and 4 . This is in contrast to the case of polysilicon film 32 having a large number of crystals as shown in FIG.
- the isotropic etching agentruns along grain boundaries to reach gate insulating film 4 .
- the isotropic etching agentdoes not run along grain boundaries to reach gate insulating film 4 .
- a 2-power supply semiconductor device including a plurality of field effect transistors according to a second variation of the seventh embodimenthas basically the same structure as the 2-power supply semiconductor device according to the seventh embodiment shown in FIG. 56 , with different being that the first gate electrode 31 a is formed only of doped polysilicon film as shown in FIG. 64 , and that the second gate electrode 32 a is formed only of doped polysilicon film. Since the first and second gate electrodes 31 a and 32 a are formed of doped polysilicon films, respectively, the method of forming doped polysilicon film 7 (see FIG. 56 ) in the 2-power supply semiconductor device according to the seventh embodiment can be omitted. Thus, the manufacturing process can be simplified as compared to the 2-power supply semiconductor device according to the seventh embodiment.
- isolation oxide film 2is formed to surround an active region on the main surface of p type semiconductor substrate.
- Second gate insulating film 4is formed on the active region of the main surface of semiconductor substrate 1 .
- Doped polysilicon film 32is formed on second gate insulating film 4 and isolation oxide film 2 .
- a resist pattern 5 fis formed on doped polysilicon film 32 positioned in the high Vdd region.
- the thickness of doped polysilicon film 32has such a thickness to be used as a gate electrode.
- First gate insulating film 6(see FIG. 67 ) is formed on the main surface of semiconductor substrate 1 and on doped polysilicon film 32 .
- Doped polysilicon film 31(see FIG. 67 ) is formed on first gate insulating film 6 .
- a resist pattern 5 j(see FIG. 67 ) is formed in the portion positioned in the low Vdd region on doped polysilicon film 31 .
- an oxidizing step to form first gate insulating film 6may be performed using doped polysilicon film 32 as a mask before forming second gate electrode 32 a (see FIG. 64 ).
- a lower part of a side of second gate electrode 32 acan be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- Doped polysilicon film 31 and first gate insulating film 6 positioned in the high Vdd regionare etched away, using resist pattern 5 j as a mask, followed by removal of resist pattern 5 j , and the structure as shown in FIG. 68 thus results.
- resist patterns 5 g and 5 hare formed on doped polysilicon films 31 and 32 .
- first and second gate electrodes 31 a and 32 aare formed only of doped polysilicon films 31 and 32 (see FIG. 69 ) serving as a protection conductive film, the number of steps for forming the doped polysilicon films can be reduced as compared to the process of manufacturing the 2-power supply semiconductor device according to the seventh embodiment shown in FIGS. 57 to 60 .
- An impurityis then introduced into a prescribed region of the main surface of semiconductor substrate 1 followed by formation of a sidewall oxide film 9 (see FIG. 64 ) on sides of first and second gate electrodes 31 a and 32 a (see FIG. 64 ), and the semiconductor device as shown in FIG. 64 results.
- the second variation of the fourth embodimentafter oxidizing the main surface of semiconductor substrate 1 positioned in the low Vdd region before forming first gate insulating film 6 , a part of the surface is isotropically etched to prevent the quality of gate insulating film 6 from deteriorating.
- doped polysilicon films 31 and 32 serving as a protection conductive film to protect the gate insulating filmsmay be formed on first and second gate insulating films 6 and 4 to bring about the same effect as the seventh embodiment.
- a 2-power supply semiconductor device including a plurality of field effect transistorsthere are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistors supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- low Vdd regionthere are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 , a pair of impurity diffusion regions 8 , spaced apart from each other and having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration n type impurity diffusion region 10 formed adjacent to n type impurity diffusion region 8constitute an LDD structure.
- a first gate insulating film 6is formed on the first channel region.
- a doped polysilicon film 31is formed on first gate insulating film 6 .
- a nitride film 27is formed on doped polysilicon film 31 .
- a doped polysilicon film 7is formed on nitride film 27 .
- Doped polysilicon films 31 and 7 , and nitride film 27form a first gate electrode 18 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- the first source/drain regions 10 , impurity diffusion regions 8 , first gate insulating film 6 , and first gate electrode 18form the first field effect transistor.
- a pair of second source/drain regions 17 , and a pair of impurity diffusion regions 16spaced apart from each other and having a second channel region therebetween.
- Low concentration, n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the second channel region.
- a doped polysilicon film 32is formed on second gate insulating film 4 .
- Nitride film 27is formed on doped polysilicon film 32 .
- Doped polysilicon films 7 and 32 and nitride film 27form second gate electrode 19 .
- Sidewall oxide film 9is formed on a side of second gate electrode 19 .
- Second source/drain regions 17 , impurity diffusion regions 16 , second gate insulating film 4 and second gate electrode 19form the second field effect transistor.
- doped polysilicon film 32is formed on second gate insulating film 4 , an oxidizing step to form first gate insulating film 6 , using doped polysilicon film 32 as a mask can be performed before forming second gate electrode 19 .
- a lower part of a side of second gate electrode 19can be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- nitride film 27is formed on doped polysilicon films 31 and 32 serving as a protection conductive film, a natural oxide film difficult to control in thickness can be prevented from being formed on doped polysilicon films 31 and 32 .
- the fluctuation of the thicknesses of doped polysilicon films 31 , 32 and 7 caused by such a natural oxide filmcan be prevented.
- the amount of overetchingcan be reduced in etching to form first and second gate electrodes 18 and 19 .
- damages to semiconductor substrate 1 positioned under doped polysilicon films 31 and 32 to be etched away, caused by overetchingcan be prevented.
- doped polysilicon films 31 and 32are nitrided by lamp annealing as shown in FIG. 72 , and nitride film 27 serving as an oxidation protection film is formed.
- doped polysilicon film 32is formed on second gate insulating film 4 , and therefore an oxidizing step to form first gate insulating film 6 can be performed using doped polysilicon film 32 as a mask before forming second gate electrode 19 .
- a lower part of a side of second gate electrode 19can be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- nitride film 27is formed on the surfaces of doped polysilicon films 31 and 32 , a natural oxide film difficult to control in thickness can be prevented from being formed on doped polysilicon films 31 and 32 .
- variations of the thicknesses of doped polysilicon films 31 , 32 and 7 caused by such a natural oxide filmcan be prevented.
- the amount of overetching during etching to form first and second gate electrodes 18 and 19can be reduced.
- damages caused by overetching to semiconductor substrate 1 positioned under doped polysilicon films 31 and 32 to be etched awaycan be prevented.
- doped polysilicon film 7is formed in the low Vdd region and the high Vdd region.
- Resist patternsare thereafter formed on doped polysilicon film 7 , anisotropic etching is performed using the resist patterns as a mask to form first and second gate electrodes 18 and 19 (see FIG. 71 ).
- An impurityis introduced into the main surface of semiconductor substrate 1 , followed by formation of a sidewall oxide film 9 (see FIG. 71 ) on sides of first and second gate electrodes 18 and 19 , and the semiconductor device as shown in FIG. 71 is thus obtained.
- a 2-power supply semiconductor device including a plurality of field transistorsthere are formed, on a main surface of a p type semiconductor substrate 1 , a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other.
- An isolation oxide film 2is formed between the first and second field effect transistors.
- first source/drain regions 10there are formed, on the main surface of substrate 1 , a pair of first source/drain regions 10 , and a pair of impurity diffusion regions 8 , spaced apart from each other and having a first channel region therebetween.
- Low concentration, n type impurity diffusion region 8 formed adjacent to the first channel region and high concentration, n type impurity diffusion region 10 formed adjacent to n type impurity region 8constitute an LDD structure.
- a first gate insulating film 25is formed on the first channel region.
- a first gate electrode 18is formed on first insulating film 25 .
- a sidewall oxide film 9is formed on a side of first gate electrode 18 .
- First source/drain regions 10 , impurity diffusion regions 8 , first gate insulating film 25 , and first gate electrode 18form the first field effect transistor.
- n type impurity diffusion region 16 formed adjacent to the second channel region and high concentration, n type impurity diffusion region 17 formed adjacent to n type impurity diffusion region 16constitute an LDD structure.
- a second gate insulating film 4is formed on the second channel region.
- a second gate electrode 19is formed on second gate insulating film 4 .
- Sidewall oxide film 9is formed on a side of second gate electrode 19 .
- Second source/drain regions 17 , impurity diffusion regions 16 , second gate insulating film 4 and second gate electrode 19form the second field effect transistor.
- first gate insulating film 25is isotropically etched to be reduced in thickness. Therefore, first gate insulating film 25 can be formed before forming second gate electrode 19 . As a result, a lower part of a side of second gate electrode 19 can be prevented from being oxidized in the step of oxidizing to form first gate insulating film 25 , and a gate bird's beak caused by the oxidation can be prevented. Therefore, the threshold voltages of the field effect transistors can be prevented from increasing.
- isolation oxide film 2is formed to surround an active region on the main surface of p type semiconductor substrate 1 .
- Second gate insulating film 4is formed on the active region of the main surface of semiconductor substrate 1 .
- a resist pattern 5 fis formed on second gate insulating film 4 and isolation oxide film 2 , positioned in the high Vdd region.
- first gate insulating film 25thinner than second gate insulating film 4 positioned in the high Vdd region.
- First and second gate insulating films 25 and 4are formed thicker than their final thickness when used as the gate insulating films for the field effect transistors.
- the difference between second gate insulating film 4 and first gate insulating film 25 in thicknessis set substantially identical to the final difference in thickness between the first and second gate insulating films used in the field effect transistors.
- Resist pattern 5 fis then removed to obtain the structure as shown in FIG. 75 .
- first and second gate insulating films 25 and 4are isotropically etched to remove the defects formed by the removal of the resist pattern.
- the first and second gate insulating films 25 and 4are isotropically etched to have the thicknesses of the gate insulating films used in the first and second field effect transistors.
- first and second gate insulating films 25 and 4are formed of a single insulating film, only a single oxidizing step is necessary to form first and second gate insulating films 25 and 4 .
- the number of oxidizing stepscan be reduced by one, and the process of manufacturing the semiconductor device can thus be simplified.
- the first and second gate insulating filmsare formed by means of isotropic etching, possible defects such as local irregularities caused by the removal of resist pattern 5 f (see FIG. 74 ) present on the surface of second gate insulating films 4 can be removed by the isotropic etching process.
- the first and second gate insulating films 25 and 4will be highly reliable, and the fluctuation of the threshold voltages of the field effect transistors can be prevented.
- a doped polysilicon film 3is then formed on first and second gate insulating films 25 and 4 , and on isolation oxide film 2 .
- Resist patterns 5 b and 5 hare formed on doped polysilicon film 3 .
- first and second gate electrodes 18 and 19are anisotropically etched away to form first and second gate electrodes 18 and 19 (see FIG. 77 ), followed by removal of resist patterns 5 g and 5 h .
- an impurityis then introduced into the main surface of semiconductor substrate 1 , using first and second gate electrodes 18 and 19 as masks, n type impurity diffusion regions 8 and 16 are formed on the main surface of semiconductor substrate 1 .
- the oxidizing step to form first and second gate insulating films 25 and 4can be performed before forming second gate electrode 19 , a lower part of a side of the gate electrode can be prevented from being oxidized, and a gate bird's beak can be avoided.
- the threshold voltages of the field effect transistorscan be prevented from increasing.
- electrical characteristics of the semiconductor device including the plurality of field effect transistorscan be prevented from deteriorating.
- a sidewall oxide film 9is then formed on sides of first and second gate electrodes 18 and 19 as shown in FIG. 78 .
- impurity ionsare introduced into the main surface of semiconductor substrate 11 to form high concentration, n type impurity diffusion regions 10 and 17 .
- the semiconductor device as shown in FIG. 73is thus obtained.
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Abstract
Description
- 1. Field of the Invention
- The present invention relates generally to semiconductor devices and manufacturing methods thereof, and more particularly, to a semiconductor device including a plurality of field effect transistors and a manufacturing method thereof.
- 2. Description of the Background Art
- In recent years, as semiconductor devices came to be more densely integrated and reduced in size, 2-power supply devices having external voltage of a conventional level and internal voltage of a lower level have been proposed.
FIG. 79 is a cross sectional view showing such a conventional 2-power supply semiconductor device including a plurality of field effect transistors.- Referring to
FIG. 79 , the conventional 2-power supply semiconductor device include a first field effect transistor supplied with first power supply voltage (low Vdd) and a second field effect transistor supplied with second power supply voltage (high Vdd) higher than low Vdd formed on a main surface of a ptype semiconductor substrate 101 and spaced apart from each other. Anisolation oxide film 102 is formed between the first and second field effect transistors. - In the low Vdd region, a pair of first source/
drain regions 110 and a pair of low concentrationimpurity diffusion regions 108 are formed spaced apart from each other on the main surface ofsemiconductor substrate 101 having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 108 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 110 formed adjacent to n typeimpurity diffusion region 108 constitute an LDD (Lightly Doped Drain) structure. A first gateinsulating film 106 is formed on the first channel region. Afirst gate electrode 118 is formed on firstgate insulating film 106. Asidewall oxide film 109 is formed on a side offirst gate electrode 118. The first field effect transistor supplied with low Vdd is formed of first source/drain regions 110,impurity diffusion regions 108, first gateinsulating film 106, andfirst gate electrode 118. - In the high Vdd region, a pair of second source/
drain regions 117 and a pair of low concentrationimpurity diffusion regions 116 are formed on the main surface ofsemiconductor substrate 101, spaced apart from each other and having a second channel region therebetween. Second source/drain region 117 and low concentrationimpurity diffusion region 116, in other words low concentration n typeimpurity diffusion region 116 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 117 formed adjacent to n typeimpurity diffusion region 116 constitute an LDD structure. A secondgate insulating film 104 is formed on the second channel region. Firstgate insulating film 106 is formed on secondgate insulating film 104. Asecond gate electrode 119 is formed on firstgate insulating film 106. Asidewall oxide film 120 is formed on a side ofsecond gate electrode 119. Second source/drain regions 117 andimpurity diffusion region 116, second gateinsulating film 104, first gateinsulating film 106 andfirst gate electrode 119 form the second field effect transistor supplied with high Vdd. Thegate insulating films insulating film 106 of first field effect transistor supplied with low Vdd. - Referring to FIGS.80 to86, a method of manufacturing the conventional 2-power supply semiconductor device will be now described.
Isolation oxide film 102 is formed on the main surface ofsemiconductor substrate 101 to surround an active region. Secondgate insulating film 104 is formed on the active region on the main surface ofsemiconductor substrate 101. Aresist pattern 105ais formed on secondgate insulating film 104 positioned in the high Vdd region and onisolation oxide film 102. The structure as shown inFIG. 80 is thus obtained.- An isotropic etching is performed using
resist pattern 105aas a mask to remove secondgate insulating film 104 positioned in the low Vdd region to obtain the structure as shown inFIG. 81 .Resist pattern 105ais then removed. - As shown in
FIG. 82 , first gateinsulating film 106 is formed on the main surface ofsemiconductor substrate 101 and on second gateinsulating film 104. - A first doped polysilicon film103 (see
FIG. 83 ) is deposited on first gateinsulating film 106 andisolation oxide film 102.Resist patterns polysilicon film 103 to be first andsecond gate electrodes 118 and119 (seeFIG. 79 ). The structure as shown inFIG. 83 is thus obtained. - Then, using
resist patterns polysilicon film 103, and first andsecond gate electrodes Resist patterns FIG. 84 is thus obtained. The gate insulating film portion of the second field effect transistor formed of first and second gateinsulating films gate insulating film 106 of the first field effect transistor. Thus, the breakdown voltage of the second field effect transistor can be greater than the breakdown voltage of the first field effect transistor, so that the second field effect transistor may be supplied with voltage higher than the first field effect transistor. - As shown in
FIG. 85 , an n type impurity is introduced into a prescribed region of the main surface ofsemiconductor substrate 101 to form low concentration n typeimpurity diffusion regions Sidewall oxide films 109 and120 (seeFIG. 86 ) are formed on sides of first andsecond gate electrodes semiconductor substrate 101 to form high concentration n typeimpurity diffusion regions FIG. 86 .- The conventional 2-power supply semiconductor device is manufactured as described above.
- In the manufacture of the 2-power supply semiconductor device,
resist pattern 105ais directly formed on second gateinsulating film 104 positioned in the high Vdd region. In the following removal ofresist pattern 105a, defects (local irregularities) are sometimes generated in the surface of second gateinsulating film 104. A light etching processing for removingresist pattern 105ais directly performed to the surface of secondgate insulating film 104, second gateinsulating film 104 may be reduced in thickness. The defects in the surface of secondgate insulating film 104 and the reduction in thickness lead to a reduction in the breakdown voltage of secondgate insulating film 104, and as a result electrical characteristics of the semiconductor device including the field effect transistor deteriorate. - As a countermeasure, a manufacturing method as shown in FIGS.87 to93 has been proposed.
- Referring to FIGS.87 to93, the proposed conventional method of manufacturing a 2-power supply semiconductor device including a plurality of field effect transistors will be described.
Isolation oxide film 102 is formed on the main surface of ptype semiconductor substrate 101 to surround an active region. Secondgate insulating film 104 is formed on the active region in the main surface of ptype semiconductor substrate 101. First dopedpolysilicon film 103 is formed on secondgate insulating film 104 andisolation oxide film 102.Resist pattern 105ais formed on the region of firstdoped polysilicon film 103 to be second gate electrode119 (seeFIG. 88 ) positioned in the high Vdd region to obtain the structure as shown inFIG. 87 .- An anisotropic etching is performed using
resist pattern 105aas a mask to etch away a part of first dopedpolysilicon film 103, andsecond gate electrode 119 as shown inFIG. 88 results.Resist pattern 105ais then removed.Resist pattern 105bis formed on second gateinsulating film 104 positioned in the high Vdd region andsecond gate electrode 119 to form the structure as shown inFIG. 88 . - In the manufacture,
second gate electrode 119 is formed on second gateinsulating film 104 and thenresist pattern 105bis formed.Resist pattern 105bis not directly formed on the region of the surface of secondgate insulating film 104 in contact withsecond gate electrode 119. Thus, defects in the surface of secondgate insulating film 104 as in the manufacturing method shown in FIGS.80 to86 can be prevented. - Then, as shown in
FIG. 89 , second gateinsulating film 104 positioned in the low Vdd region is removed by an isotropic etching. Then,resist pattern 105bis removed. - As shown in
FIG. 90 , a silicon oxide film to be firstgate insulating film 106 is formed on the main surface of ptype semiconductor substrate 101 positioned in the low Vdd region and on second gateinsulating film 104 andsecond gate electrode 119. - Then, on first gate
insulating film 106 andisolation oxide film 102, a second doped polysilicon film107 (seeFIG. 91 ) is formed by means of CVD.Resist pattern 105c(seeFIG. 91 ) is formed on the region of second dopedpolysilicon film 107 to be first gate electrode118 (seeFIG. 93 ). The structure as shown inFIG. 91 is thus obtained. - An anisotropic etching is performed using resist
pattern 105cas a mask to remove a part of second dopedpolysilicon film 107, and first gate electrode118 (seeFIG. 92 ) is formed as a result. After the anisotropic etching, a part of second dopedpolysilicon film 107 also remains on a side ofsecond gate electrode 119. Resistpattern 105cis then removed. Resistpattern 105d(seeFIG. 92 ) is formed on firstgate insulating film 106 positioned in the low Vdd region and onfirst gate electrode 118. Thus, the structure as shown inFIG. 92 results. - Second doped
polysilicon film 107 remaining on the side of second gate electrode is removed by an isotropic etching, and then resistpattern 105dis removed. After low concentration, n typeimpurity diffusion regions 108,116 (seeFIG. 93 ) are formed by introducing an impurity,sidewall oxide films 109,120 (seeFIG. 93 ) are formed, followed by formation of high concentration n typeimpurity diffusion regions 110,117 (seeFIG. 93 ), and the semiconductor device as shown inFIG. 93 results. - In the manufacture of the proposed conventional 2-power supply semiconductor device as shown in FIGS.87 to93,
second gate electrode 119 is formed before resistpattern 105bis formed as shown inFIG. 88 , in order to prevent defects from being formed in the surface of secondgate insulating film 104. In the manufacture of the 2-power supply semiconductor device, however, in the step as shown inFIG. 90 , during forming firstgate insulating film 106,second gate electrode 119 formed of doped polysilicon is oxidized in anend 123 of the contact portion betweensecond gate electrode 119 and secondgate insulating film 104 as shown inFIG. 94 . Therefore, asilicon oxide film 124 grows along the contact surface between secondgate insulating film 104 andsecond gate electrode 119. Thus grown silicon oxide film is called “gate bird's beak”. Herein,FIG. 94 is an enlarged view ofregion 110 shown inFIG. 90 . The gate oxide film having a “gate bird's beak” formed of an oxide film is poor in quality and difficult to control in thickness. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors deteriorate. - The present invention is directed to a solution to the above-described problems. It is one object of the invention to provide a semiconductor device which can prevent electrical characteristics of the device from deteriorating by preventing the deterioration of the quality of a gate insulating film.
- Another object of the invention is to provide a semiconductor device which can prevent a gate bird's beak from being generated.
- Yet another object of the invention is to provide a method of manufacturing a semiconductor device which can prevent the deterioration of the quality of a gate insulating film.
- A semiconductor device according to one aspect of the invention having a plurality of field effect transistors includes first and second field effect transistors.
- The first field effect transistor includes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode. The second field effect transistor includes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode. The first source/drain regions are formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween. The first gate insulating film is formed on the first channel region in a first thickness. The second source/drain regions are formed on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween. The second gate insulating film is formed on the second channel region in a second thickness larger than the first thickness. The second gate electrode is formed on the second gate insulating film. An oxidation protection film to prevent one of the first and second gate electrodes from being oxidized is formed on a side of one of the gate electrodes. In the semiconductor device according to this aspect, the oxidation protection film to prevent the gate electrode from being oxidized is formed on a side of one of the first and second gate electrodes, and therefore an oxidizing step to form a gate insulating film of another field effect transistor may be performed while the oxidization protection film is formed on a side of that one gate electrode. As a result, the lower part of the side of the gate electrode can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- A semiconductor device according to another aspect of the invention having a plurality of field effect transistors includes first and second field effect transistors.
- The first field effect transistor includes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode. The second field effect transistor includes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode. The first source/drain regions are formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween. The first gate insulating film has a first thickness and is formed on the first channel region to include an oxide nitride film. The first gate electrode is formed on the first gate insulating film. The second source/drain regions are formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween. The second gate insulating film is formed on the second channel region and has a second thickness larger than the first thickness. The second gate electrode is formed on the second gate insulating film.
- In the semiconductor device according to this aspect, since the first gate insulating film is formed to include the oxide nitride film, in the manufacturing process which will be described, in the presence of the second gate electrode, during forming the oxide nitride film to be the first gate insulating film, an end of the second gate electrode can be prevented from being excessively oxidized in the contact portion between a lower part of a side of the second gate electrode and the second gate insulating film. Thus, as a result, the lower part of the side of the gate electrode can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. Furthermore, since the first gate insulating film is formed to include the oxide nitride film, the first gate insulating film may be formed thinner with a prescribed breakdown voltage being maintained than the case of using a conventional silicon oxide film or the like. As a result, the driving voltage of the first field effect transistor may be reduced.
- A semiconductor device according to another aspect of the invention having a plurality of field effect transistors includes first and second field effect transistors. The first field effect transistor includes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode. The second field effect transistor includes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode. The first source/drain regions are formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween. The first gate insulating film is formed on the first channel region and has a first thickness. The first gate electrode is formed on the first gate insulating film. The second source/drain regions are formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween. The gate insulating film is formed on the second channel region and has a second thickness larger than the first thickness. The second gate electrode is formed on the second gate insulating film. An anti-oxidation conductive film is formed on at least one of the first and second gate insulating films.
- In the semiconductor device according to this aspect, the anti-oxidation conductive film is formed on at least one of the first and second gate insulating films, it is not necessary to form a resist pattern directly on the surface of one of the first and second gate insulating films in the following manufacturing steps. Furthermore, before forming one of the first and second gate electrodes, an oxidizing step to form the other one of the first and second gate insulating films may be performed using the anti oxidation conductive film. Thus, in the step of oxidizing the first gate insulating film, a lower part of the side of one of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- Furthermore, since the anti-oxidation conductive film is formed on one of the first and second gate insulating films, a resist pattern will not be formed directly on one of the first and second gate insulating films in the following manufacturing steps. As a result, defects such as local irregularities in the gate insulating film as formed during removing the resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating.
- In the semiconductor device according to this aspect, a semiconductor film having a conductive impurity may be formed at a position between the anti-oxidation conductive film and at least one of the first and second gate insulating films.
- Thus, when voltage is supplied to one of the first and second gate electrodes having the semiconductor film including the conductive impurity, the formation of a depletion layer caused by a reduction in the concentration of the conductive impurity in the vicinity of one of the first and second gate insulating films may be prevented. As a result, the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layer can be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- A semiconductor device according to another aspect of the invention having a plurality of field effect transistors includes first and second field effect transistors.
- The first field effect transistor includes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode. The second field effect transistor includes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode. The first source/drain regions are formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween. The first gate insulating film is formed on the first channel region and has a first thickness. The first gate electrode is formed on the first gate insulating film. The second source/drain regions are formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween. The second gate insulating film is formed on the second channel region and has a second thickness. The second gate electrode is formed on the second gate insulating film. A semiconductor film having a conductive impurity is formed on and in contact with at least one of the first and second gate insulating films. An anti-oxidation insulating film for preventing the semiconductor film having the conductive impurity from being oxidized is formed on the semiconductor film.
- Since the semiconductor film having the conductive impurity is thus formed on and in contact with one of the first and second gate insulating films, it is not necessary to form a resist pattern directly on a surface of one of the first and second gate insulating films in the manufacture of the semiconductor device. Furthermore, before one of the first and second gate electrodes is formed, an oxidizing step to form the other one of the first and second gate insulating films may be performed using the anti-oxidation insulating film as a mask. In the step of oxidizing the gate insulating films, a lower part of a side of the gate electrodes can be prevented from being oxidized as a result, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- Furthermore, the semiconductor film having the conductive impurity is formed on and in contact with one of the first and second gate insulating films, a resist pattern is not formed directly on one of the first and second gate insulating films. As a result, defects such as local irregularities in the gate insulating films as formed during removing the resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating. Furthermore, when voltage is supplied to one of the first and second gate electrodes having the semiconductor film including the conductive impurity, the formation of a depletion layer caused by a reduction in the concentration of the conductive impurity in the vicinity of one of the first and second gate insulating films may be prevented. As a result, the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layer can be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- A semiconductor device according to another aspect of the invention having a plurality of field effect transistors includes first and second field effect transistors.
- The first field effect transistor includes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode. The second field effect transistor includes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode. The second gate electrode has a first conductive film, an insulating film and a second conductive film. The first source/drain regions are formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween. The first gate insulating film is formed on the first channel region and has a first thickness. The first gate electrode is formed on the first gate insulating film. The second source/drain regions are formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween. The second gate insulating film is formed on the second channel region and has a second thickness. The first conductive film to be a part of the second gate electrode is formed on the second gate insulating film. The insulating film to be a part of the second gate electrode is formed on the first conductive film. The second conductive film to be a part of the second gate electrode is formed on the insulating film.
- Thus, the second gate electrode has the first conductive film, the insulating film, and the second conductive film, and therefore an oxidizing step for forming the first gate insulating film can be performed before forming the second gate electrode without forming a resist pattern directly on the surface of the second gate insulating film. As a result, a lower part of a side of the gate electrode can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- A semiconductor device according to another aspect of the invention having a plurality of field effect transistors includes first and second field effect transistors.
- The first field effect transistor includes a pair of first source/drain regions, a first gate insulating film, and a first gate electrode. The second field effect transistor includes a pair of second source/drain regions, a second gate insulating film, and a second gate electrode. The first source/drain regions are formed, on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween. The first gate insulating film is formed on the first channel region and has a first thickness. The first gate electrode is formed on the first gate insulating film. The second source/drain regions are formed, on the main surface of the semiconductor substrate, spaced apart from each other and having a second channel region therebetween. The second gate insulating film is formed on the second channel region and has a second thickness larger than the first thickness. The second gate electrode is formed on the second gate insulating film. A protection conductive film is formed on and in contact with at least one of the first and second gate insulating films.
- Thus, the protection conductive film is formed on and in, contact with one of the first and second gate insulating films, it is not necessary to form a resist pattern directly on the surface of one of the first and second gate insulating films. Furthermore, before forming one of the first and second gate electrodes, an oxidizing step for forming the other one of the first and second gate insulating films can be performed using the protection conductive film. Thus, in the step of oxidizing the gate insulating films, a lower part of a side of one of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- In the semiconductor device according to this aspect, the protection conductive film includes first and second protection conductive films. The first protection conductive film may be formed on and in contact with the first gate insulating film, while the second protection conductive film may be formed on and in contact with the second gate insulating film. The first and second protection conductive films may be substantially equal in thickness.
- Thus, during etching the first and second protection conductive films to form the first and second gate electrodes, the part of the thickness of the first and second protection conductive films to be removed by the etching can be made substantially equal in the regions to form the first and second gate electrodes. As a result, during the etching for forming the first and second gate electrodes, the amount of etching for forming the first gate electrode can be substantially the same as the amount of etching for forming the second gate electrode. Therefore, the amount of overetching during forming the first and second gate electrodes can be reduced. As a result, the semiconductor substrate or the like positioned under the protection conductive films to be etched away can be prevented from being damaged by overetching. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- The semiconductor device according to this aspect may further include a protection conductive film formed by depositing a film having an amorphous structure. Thus, the film having the amorphous structure is free from grain boundaries, and therefore during isotropically etching the protection conductive film in the manufacture of the semiconductor device, damages to the gate insulating film positioned under the protection conductive film caused by the isotropic etching agent running along grain boundaries can be prevented. As a result, the fluctuation of the threshold voltages of the field effect transistors can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented.
- In the semiconductor device according to this aspect, an anti-oxidation film may be formed on and in contact with the protection conductive film. Thus, in the manufacture of the semiconductor device, a natural oxide film difficult to control in thickness can be prevented from being formed on the protection conductive film. Thus, in an etching step to form the first and second gate electrodes, the variation of the thickness of the protection conductive film to be etched away caused by the formation of such a natural oxide film can be prevented. As a result, during etching for forming the first and second gate electrodes, the variation of the thickness of the protection conductive film to be etched away can be reduced, the amount of overetching, can be reduced. As a result, damages to the semiconductor substrate or the like positioned under the protection conductive film to be etched away, caused by overetching can be prevented.
- In a method of manufacturing a semiconductor device according to another aspect of the invention, a first gate insulating film having a first thickness is formed on a main surface of a semiconductor device. A first gate electrode is formed on the first gate insulating film. Using the gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween. A second gate insulating film having a second thickness larger than the first thickness is formed on the main surface of the semiconductor substrate. Using the second gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween. An oxidation protection film to prevent a gate electrode from being oxidized is formed on a side of one of the first and second gate electrodes. After one of the first and second gate insulating films is formed, the other one of the first and second gate insulating films is formed with the oxidation protection film being present on the side of the gate electrode formed on that one of the first and second gate insulating films.
- Thus, with the gate electrode being formed on one of the first and second gate insulating films, the other one of the first and second gate insulating films is formed, and therefore resist pattern is not directly formed on the gate insulating film. Therefore, during the following removal of the resist pattern, a direct light etching processing can be prevented on the surface of the gate insulating film. As a result, defects in the surface of the gate insulating film caused by such a light etching processing can be prevented. Furthermore, with the oxidation protection film for preventing a gate electrode from being oxidized being present on a side of one of the first and second gate electrodes, an oxidizing step to form the other one of the first and second gate insulating films is performed. As a result, a lower part of a side of the gate electrode can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- In a method of manufacturing a semiconductor device according to another aspect of the invention, a first gate insulating film including an oxide nitride film and having a first thickness is formed on a main surface of a semiconductor substrate. A first gate electrode is formed on the first gate insulating film. Using the gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween. A second gate insulating film having a second thickness larger than the first thickness is formed on the main surface of the semiconductor substrate. Using the second gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween. The first gate insulating film is formed in the presence of the second gate electrode formed on the second gate insulating film.
- Thus, while the second gate electrode has been formed on the second gate insulating film, the first gate insulating film is formed, and therefore resist pattern is not directly formed on the second gate insulating film. Therefore, during the following removal of the resist pattern, a direct light etching processing on the surface of the second gate insulating films can be prevented. Thus, defects in the surface of the second gate insulating film caused by such a light etching processing can be prevented.
- Furthermore, since there is the step of forming the first gate insulating film to include the oxide nitride film, an end of the second gate electrode can be suppressed from being excessively oxidized at the joint of a lower part of a side of the second gate electrode and the second gate insulating film during forming the oxide nitride film to be the first gate insulating film while the second gate electrode has been formed. Thus, a gate bird's beak can be avoided. Therefore, the threshold voltages of the field effect transistors can be prevented increasing, and as a result electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. Since the first gate insulating film is formed to include the oxide nitride film, the thickness of the first gate insulating film can be made smaller than the case of using a conventional silicon oxide film as a prescribed breakdown voltage is maintained. As a result, the driving voltage of the first field effect transistor can be reduced.
- In a method of manufacturing a semiconductor device according to another aspect of the invention, a first gate insulating film having a first thickness is formed on a main surface of a semiconductor substrate. A first gate electrode is formed on the first gate insulating film. Using the first gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween. A second gate insulating film having a second thickness larger than the first thickness is formed on the main surface of the semiconductor substrate. Using the second gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween. An anti-oxidation conductive film is formed on at least one of the first and second gate insulating films. While the anti-oxidation conductive film has been formed on at least one of the first and second gate insulating films, the other one of the first and second gate insulating films is formed.
- Since the anti-oxidation conductive film is formed on one of the first and second gate insulating films, it is not necessary to directly form a resist pattern on the surface of one of the first and second gate insulating films. In addition, before forming one of the first and second gate electrodes, an oxidizing step to form the other one of the first and second gate insulating films can be performed using the anti-oxidation conductive film as a mask. As a result, a lower part of a side of one of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- Furthermore, since the anti-oxidation conductive film is formed on one of the first and second gate insulating films, a resist pattern is not directly formed on that one of the first and second gate insulating films. As a result, defects such as local irregularities in the gate insulating film as formed during removing a resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating.
- The method of manufacturing the semiconductor device according to this aspect may further include the step of forming a semiconductor film including a conductive impurity at a position between the anti-oxidation conductive film and at least one of the first and second gate insulating films. Thus, when voltage is supplied to one of the first and second gate electrodes on the side having the semiconductor film including the conductive impurity, the formation of a depletion layer caused by a reduction in the concentration of the conductive impurity in the vicinity of one of the first and second gate insulating films can be restricted. As a result, the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layer can be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- In the method of manufacturing the semiconductor device according to this aspect, a substrate protection film may be formed in the region on the main surface of the semiconductor substrate to form one of the first and second gate insulating films. With the substrate protection film being present, the other one of the first and second gate insulating films and the anti-oxidation conductive film may be formed.
- Thus, with the presence of the substrate protection film, the other one of the first and second gate insulating films and the anti-oxidation conductive film are formed, the insulating film forming the other one of the first and second gate insulating film can be prevented from being formed in contact with the main surface of the semiconductor substrate positioned in the region to form one of the first and second gate insulating films.
- As a result, during etching away the anti-oxidation conductive film and the insulating film from the region to form one of the first and second gate insulating films, the main surface of the semiconductor substrate positioned in the region to form that one of the first and second gate insulating films can be prevented from being directly etched. Thus, damages to the main surface of the semiconductor substrate caused by etching can be prevented. As a result, during forming one of the first and second gate insulating films, the deterioration of the quality of one of the first and second gate insulating films caused by the presence of damages by the etching on the main surface of the semiconductor substrate in which the gate insulating film is formed can be prevented. As a result, the fluctuation of the threshold voltage of the field effect transistors can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented.
- The method of manufacturing the semiconductor device according to this aspect may further include the step of removing a part of the main surface of the semiconductor substrate positioned in the region to form one of the first and second gate insulating films before forming that insulating film.
- Thus, in the main surface of the semiconductor substrate positioned in the region to form one of the first and second gate insulating films by means of etching in the manufacture of the semiconductor device, a part of the main surface of the semiconductor substrate with damages such as local irregularities can be removed. Therefore, that one of the first and second gate insulating films can be formed on the main surface of the semiconductor substrate removed of the damaged part. Therefore, the quality of the gate insulating film can be prevented from deteriorating due to damages on the main surface of the semiconductor substrate. The fluctuation of the threshold voltages of the field effect transistors can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented.
- In a method of manufacturing a semiconductor device according to another aspect of the invention, a first gate insulating film having a first thickness is formed on a main surface of a semiconductor device. A first gate electrode is formed on the first gate insulating film. Using the gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween. A second gate insulating film having a second thickness larger than the first thickness is formed on the main surface of the semiconductor substrate. A first conductive film to be a part of a second electrode is formed on the second gate insulating film. An insulating film to be a part of the second gate electrode is formed on the first conductive film. A second conductive film to be a part of the second gate electrode is formed on the insulating film. The first and second insulating films and the insulating film are anisotropically etched to form the second gate electrode. Using the second gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a second pair of source/drain regions, spaced apart from each other and having a second channel region therebetween. Herein the first gate insulating film is formed in the presence of the first conductive film.
- Thus, after forming the first conductive film to be a part of the second gate electrode on the second gate insulating film, the first gate insulating film is formed, and therefore an oxidizing step to form the first gate insulating film can be performed without forming a resist pattern directly on the surface of the second gate insulating film. Therefore, during the following removal of the resist pattern, a direct light etching processing to the surface of the second gate insulating film can be prevented. Thus, defects on the surface of the second gate insulating film caused by such a light etching processing can be prevented.
- In the presence of the first conductive film, after the first gate insulating film is formed and then the insulating film and the second conductive films are formed, the first and second conductive films and the insulating film are anisotropically etched to form the second gate electrode, a side of the second gate electrode can be prevented from being oxidized in the oxidizing step to form the first gate insulating film. Thus, a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. In the presence of the insulating film, when a voltage is supplied to the second gate electrode, the voltage drops in the insulating film, and voltage imposed on the second gate insulating film can be reduced.
- In a method of manufacturing a semiconductor device according to another aspect of the invention, a first gate insulating film having a first thickness is formed on a main surface of a semiconductor substrate. A first gate electrode is formed on the first gate insulating film. Using the gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a pair of first source/drain regions, spaced apart from each other and having a first channel region therebetween. A second gate insulating film having a second thickness larger than the first thickness is formed on the main surface of the semiconductor substrate. A second gate electrode is formed on the second gate insulating film. Using the second gate electrode as a mask, an impurity is introduced into the main surface of the substrate to form a pair of second source/drain regions, spaced apart from each other and having a second channel region therebetween. A protection conductive film for protecting a gate insulating film is formed on and in contact with at least one of the first and second gate insulating films. While the protection conductive film has been formed, the other one of the first and second gate insulating films is formed.
- Thus, the protection conductive film is formed on and in contact with one of the first and second gate insulating films, it is not necessary to directly form a resist pattern on that one of the first and second gate insulating films. Furthermore, before forming one of the first and second gate electrodes, an oxidizing step to form the other one of the first and second gate insulating films using the protection conductive film as a mask can be performed. As a result, a lower part of the side of one of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- In the method of manufacturing the semiconductor device according to this aspect, a conductive film may be formed on and in contact with the other one of the first and second gate insulating films. A resist pattern may be formed on and in contact with the conductive film and the protection conductive film. Using the resist pattern as a mask, part of the conductive film and the protection conductive film is anisotropically etched away to simultaneously form the first gate electrode and the second gate electrode.
- Thus, the resist pattern is formed on and in contact with the protection conductive film and the conductive film, part of the conductive film and the protection conductive film is anisotropically etched away using the resist pattern as a mask, and therefore the first and second gate electrodes can be formed only of the conductive film and the protection conductive film. As a result, it is not necessary to further form a conductive film to be a part of the gate electrode on the protection conductive film, the process of manufacturing the semiconductor device can be simplified.
- In a method of manufacturing a semiconductor device according to another aspect of the invention, an insulating film is formed on a main surface of a semiconductor substrate positioned in regions to form first and second field effect transistors. A resist pattern is formed on the insulating film positioned in the regions to form the second field effect transistor. Using the resist pattern as a mask, a part of the insulating film positioned in the region to form the first field effect transistor is isotropically etched away, followed by removal of the resist pattern. Thus a part of the surface of the insulating film is isotropically etched away to form first and second gate insulating films. A first gate electrode is formed on the first gate insulating film. Using the first gate electrode as a mask, an impurity is introduced into the main surface of the semiconductor substrate to form a pair of source/drain regions, spaced apart from each other and having a first channel region therebetween. A second gate electrode is formed on the second gate insulating film. Using the second gate electrode as a mask, an impurity is introduced into the main surface of the semiconductor substrate, to form a pair of second source/drain regions, spaced apart from each other and having a second channel region therebetween.
- Thus, the first and second gate insulating films are formed of a single insulating film, only a single oxidizing step is necessary to form the first and second gate insulating films. Since the first and second gate electrodes are formed after forming the first and second gate insulating films, thus first and second gate electrodes are not oxidized during forming the first and second gate insulating films. As a result, a lower part of a side of the first and second gate electrodes can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- Furthermore, since only a single oxidizing step is necessary to form the first and second gate insulating films, in other words the number of oxidizing steps to form insulating films is reduced by one as compared to the conventional method, the process of manufacturing the semiconductor device can be simplified.
- Furthermore, the first and second gate insulating films are formed by means of isotropic etching, possible defects such as local irregularities caused by for example a step of ashing during removal of the resist pattern on the insulating film to be the first and second gate insulating films can be removed by the anisotropic etching. As a result, a defectless, highly reliable gate insulating film may be obtained, and the fluctuation of the threshold voltages of the field effect transistors can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating.
- The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
FIG. 1 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a first embodiment of the invention;- FIGS.2 to10 are cross sectional views for use in illustration of the first to ninth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the first embodiment shown in
FIG. 1 ; FIG. 11 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a second embodiment of the invention;- FIGS.12 to21 are cross sectional views for use in illustration of the first to tenth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the second embodiment shown in
FIG. 11 ; FIG. 22 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a third embodiment of the invention;FIG. 23 is a cross sectional view showing a first variation of the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodiment;FIG. 24 is a cross sectional view showing a second variation of the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodiment;- FIGS.25 to32 are cross sectional views showing the first to eighth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodiment shown in
FIG. 22 ; FIG. 33 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a fourth embodiment of the invention;- FIGS.34 to37 are cross sectional views for use in illustration of the first to fourth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment shown in
FIG. 33 ; - FIGS.38 to41 are cross sectional views for use in illustration of a process of manufacturing a 2-power supply semiconductor device including a plurality of field effect transistor according to a first variation of the fourth embodiment;
FIGS. 42 and 43 are cross sectional views for use in illustration of the first and second steps in a process of manufacturing a 2-power supply semiconductor device including a plurality of field effect transistors according to a second variation of the fourth embodiment;FIG. 44 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a third variation of the fourth embodiment;FIGS. 45 and 46 are cross sectional views for use in illustration of the first and second steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the third variation of the fourth embodiment shown inFIG. 44 ;FIG. 47 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a fifth embodiment of the invention;FIG. 48 is a cross sectional view for use in illustration of the first step in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fifth embodiment shown inFIG. 47 ;FIG. 49 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a sixth embodiment of the invention;- FIGS.50 to55 are cross sectional views for use in illustration of the first to sixth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the sixth embodiment shown in
FIG. 49 ; FIG. 56 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a seventh embodiment of the invention;- FIGS.57 to60 are cross sectional views for use in illustration of the first to fourth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the seventh embodiment shown in
FIG. 56 ; FIG. 61 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a first variation of the seventh embodiment;FIG. 62 is a view schematically showing how an isotropic etching agent runs along grain boundaries inside a dopedpolysilicon film 32 to reach a secondgate insulating film 4, when dopedpolysilicon film 32 shown inFIG. 56 is isotropically etched;FIG. 63 is a view schematically showing that an isotropic etching agent does not reach a secondgate insulating film 4 because of the absence of grain boundaries in asilicon film 34, when asilicon film 34 having an amorphous structure as shown inFIG. 61 has its surface isotropically etched in the process of manufacture;FIG. 64 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a second variation of the seventh embodiment;- FIGS.65 to70 are cross sectional views for use in illustration of the first to sixth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the second variation of the seventh embodiment shown in
FIG. 64 ; FIG. 71 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to an eighth embodiment of the invention;FIG. 72 is a cross sectional view for use in illustration of the first step in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the eighth embodiment shown inFIG. 71 ;FIG. 73 is a cross sectional view showing a 2-power supply semiconductor device including a plurality of field effect transistors according to a ninth embodiment of the invention;- FIGS.74 to78 are cross sectional views for use in illustration of the first to fifth steps in the process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the ninth embodiment shown in
FIG. 73 ; FIG. 79 is a cross sectional view showing a conventional 2-power supply semiconductor device including a plurality of field effect transistors;- FIGS.80 to86 are cross sectional views for use in illustration of the first to seventh steps in the process of manufacturing the conventional 2-power supply semiconductor device including the plurality of field effect transistors shown in
FIG. 79 ; - FIGS.87 to93 are cross sectional views for use in illustration of the first to seventh steps in the process of manufacturing another conventional 2-power supply semiconductor device including a plurality of field effect transistors; and
FIG. 94 is an enlarged view ofregion 100 inFIG. 90 .- Embodiments of the invention will be now described in conjunction with the accompanying drawings.
- First Embodiment
- Referring to
FIG. 1 , in a 2-power supply semiconductor device including a plurality of field transistors according to a first embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10, and a pair of low concentration,impurity diffusion regions 8 adjacent thereto, spaced apart from each other and having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity region 8 constitute an LDD structure. A firstgate insulating film 6 is formed on the first channel region. Afirst gate electrode 18 is formed on firstinsulating film 6. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10, low concentrationimpurity diffusion regions 8 adjacent thereto, firstgate insulating film 6, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17 and a pair of low concentrationimpurity diffusion regions 16 adjacent thereto, spaced apart from each other and having a second channel therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the second channel region. Asecond gate electrode 19 is formed on the second gate insulating film. On a side ofsecond gate electrode 19, asidewall nitride film 21 formed of a silicon nitride film which serves as an oxidation protection film to preventsecond gate electrode 19 from being oxidized is formed. On a side ofsidewall nitride film 21, asidewall oxide film 20 is formed. Second source/drain regions 17, low concentrationimpurity diffusion regions 16 adjacent thereto, secondgate insulating film 4 andsecond gate electrode 19 form the second field effect transistor. Herein, the thickness ofgate insulating film 4 of the second field effect transistor supplied with high Vdd should be larger than the thickness of thegate insulating film 6 of the first field effect transistor supplied with low Vdd. - Thus,
sidewall nitride film 21 serving as an oxidation protection film to preventsecond gate electrode 19 from being oxidized is formed on a side ofsecond gate electrode 19, and therefore an oxidizing step to form firstgate insulating film 6 in the first field effect transistor can be performed withsidewall nitride film 21 present on the side ofsecond gate electrode 19. As a result, a lower part of a side of thesecond gate electrode 19 can be prevented from being oxidized, and a gate bird's beak can be avoided. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - In addition, the sidewall is formed of a silicon nitride film, which has a higher ability of preventing diffusion of oxygen atoms than a silicon oxide film, can more surely prevent
second gate electrode 19 from being oxidized. - Referring to FIGS.2 to10, a process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the first embodiment of the invention will be described.
- As shown in
FIG. 2 ,isolation oxide film 2 is formed on the main surface of ptype semiconductor substrate 1 to surround an active region. Secondgate insulating film 4 is formed on the active region of the main surface of ptype semiconductor substrate 1. A first dopedpolysilicon film 3 is formed on secondgate insulating film 4 and onisolation oxide film 2. A resistpattern 5ais formed on a region of first dopedpolysilicon film 3 positioned in the high Vdd region to be second gate electrode19 (seeFIG. 1 ). - Using resist
pattern 5aas a mask, a part of first dopedpolysilicon film 3 is anisotropically etched away to formsecond gate electrode 19 as shown inFIG. 3 , followed by removal of resistpattern 5a(seeFIG. 2 ). Asilicon nitride film 11 is formed on secondgate insulating film 4,second gate electrode 19 andisolation oxide film 2. Silicon nitride film 11 is anisotropically etched to form, on a side ofsecond gate electrode 19,sidewall nitride film 21 formed of a silicon nitride film which serves as an oxidation protection film to preventsecond gate electrode 19 from being oxidized. A resistpattern 5bis formed on secondgate insulating film 4,second gate electrode 19 andsidewall nitride film 21 to cover the high Vdd region.- Herein, resist
pattern 5bis formed aftersecond gate electrode 19 is formed on secondgate insulating film 4, resistpattern 5bis not directly formed on the region—of the surface of secondgate insulating film 4 in whichsecond gate electrode 19 is positioned. As a result, during removing resistpattern 5b, in the region of the surface of secondgate insulating film 4, a resist removing processing or a light etching processing can be prevented. As a result, defects may be prevented from being generated in the region of the surface of secondgate insulating film 4. The condition of the anisotropic etching tosilicon nitride film 11 may be adjusted so thatsidewall nitride film 21 serving as the oxidation protection film has an arbitrary thickness. Thus, during forming second source/drain regions17 (seeFIG. 1 ) and low concentration impurity diffusion regions16 (seeFIG. 1 ) in the manufacturing process which will be described, the distance between the source region and the drain region (the length of the channel region) can be adjusted, and second source/drain regions 17 and low concentrationimpurity diffusion regions 16 having an offset structure can be readily formed. Thus, a high electric field in the vicinity of the boundary region between the channel region, second source/drain regions 17 and low concentrationimpurity diffusion regions 16 can be reduced. Thus, the generation of electrons with high energy can be prevented. As a result, the fluctuation of the threshold voltage of the second field effect transistor caused by introduction of such high energy electrons into secondgate insulating film 14 can be prevented, and as a result electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - After the step shown in
FIG. 4 , secondgate insulating film 4 present in the low Vdd region is removed by means of isotropic etching, and the structure as shown inFIG. 5 results. Thereafter, resistpattern 5bis removed. - First
gate insulating film 6 is formed on the portion of the main surface of ptype semiconductor substrate 1 positioned in the low Vdd region, on the surface of secondgate insulating film 4, and onsecond gate electrode 19 by means of thermal oxidation. Thus, the structure as shown inFIG. 6 results. Herein, the thermal oxidation to form firstgate insulating film 6 can be performed aftersidewall nitride film 21 serving as the oxidation protection film is formed on the side ofsecond gate electrode 19. As a result, a lower part of the side ofsecond gate electrode 19 can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - A second doped
polysilicon film 7 is formed to generally cover the entire surface. A resistpattern 5cis formed on the region of second dopedpolysilicon film 7 to be the first gate electrode18 (seeFIG. 1 ). As a result, the structure as shown inFIG. 7 results. - Then, using resist
pattern 5cas a mask, a part of second dopedpolysilicon film 7 is anisotropically etched away to form first gate electrode18 (seeFIG. 1 ). Herein,silicon oxide film 6 formed by the thermal oxidation during forming firstgate insulating film 6 is onsecond gate electrode 19. As a result, during the anisotropic etching for formingfirst gate electrode 18,silicon oxide film 6 serves as a stopper, so that damages such as partial removal ofsecond gate electrode 19 by the anisotropic etching can be prevented. Furthermore, second dopedpolysilicon film 7 is formed on firstgate insulating film 6, resistpattern 5d(seeFIG. 8 ) is not directly formed on first gate insulating film64 positioned under first gate electrode in the manufacturing process according to the first embodiment. Therefore, as is the case with secondgate insulating film 4, defects caused by a processing of removing a resist pattern on the surface of firstgate insulating film 6 can be prevented. Thereafter, resistpattern 5c(seeFIG. 7 ) is removed. A resistpattern 5d(seeFIG. 8 ) is formed to cover the low Vdd region. Thus, the structure as shown inFIG. 8 results. At the time, second dopedpolysilicon film 7 also remains on a side ofsidewall nitride film 21. - Second doped
polysilicon film 7 on the side ofsidewall nitride film 21 is removed by means of isotropic etching. Thereafter, resistpattern 5dis removed. An n type impurity is introduced into a prescribed region of the main surface of ptype semiconductor substrate 1 to form low concentration, n typeimpurity diffusion regions FIG. 9 . The n type impurity may be phosphorous or arsenic. Sidewall oxide films first gate electrode 18 andsidewall nitride film 21. First and secondgate insulating films second gate electrodes sidewall oxide films sidewall nitride film 21 are etched away. An n type impurity is introduced into a prescribed region of the main surface of ptype semiconductor substrate 1 to form high concentration, n typeimpurity diffusion regions FIG. 10 .- The 2-power supply semiconductor device according to the first embodiment is thus manufactured.
- Note that in the 2-power supply semiconductor device according to the first embodiment,
sidewall nitride film 21 serving as the oxidation protection film is formed on a side ofsecond gate electrode 19, the same effects can be brought about by formingsidewall nitride film 21 serving as the oxidation protection film on a side offirst gate electrode 18. - Second Embodiment
- Referring to
FIG. 11 , in a 2-power supply semiconductor device including a plurality of field transistors according to a second embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10 and a pair ofimpurity diffusion regions 26, spaced apart from each other and having a first channel region therebetween. Intermediate concentration, n typeimpurity diffusion region 26 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity region 26 constitute an LDD structure. A firstgate insulating film 6 is formed on the first channel region. Afirst gate electrode 18 is formed on firstinsulating film 6. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10,impurity diffusion regions 26, firstgate insulating film 6, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17, pairs ofimpurity diffusion regions impurity diffusion region 16 formed adjacent to the second channel region, intermediate concentration, n typeimpurity diffusion region 12 and high concentration, n type impurity-diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the second channel region. Asecond gate electrode 19 is formed on secondgate insulating film 4. Asidewall nitride film 21 serving as an oxidation protection film to preventsecond gate electrode 19 from being oxidized is formed on a side ofsecond gate electrode 19. Asidewall oxide film 20 is formed on a side ofsidewall nitride film 21. Second source/drain regions 17,impurity diffusion regions gate insulating film 4, andsecond gate electrode 19 form the second field effect transistor. Herein, the thickness of the secondgate insulating film 4 of the second field effect transistor supplied with high Vdd should be larger than the thickness of the firstgate insulating film 6 of the first field effect transistor supplied with low Vdd. - Thus, with
sidewall nitride film 21 serving as the oxidation protection film to prevent the oxidation ofsecond gate electrode 19 being present on a side ofsecond gate electrode 19, an oxidizing step to form the firstgate insulating film 6 of first field effect transistor can be performed in the manufacturing process which will be described. As a result, as is the case with the first embodiment, a gate bird's beak can be prevented from being generated insecond gate electrode 19. As a result, electric characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. Furthermore, the second source/drain regions 17 andimpurity diffusion regions impurity diffusion regions - Referring to FIGS.12 to21, a method of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the second embodiment will be described.
- As shown in
FIG. 12 ,isolation oxide film 2 to surround an active region is formed on the main surface of ptype semiconductor substrate 1. Secondgate insulating film 4 is formed on the active region of the main surface ofsemiconductor substrate 1. A first dopedpolyslicon film 3 is formed on secondgate insulating film 4 andisolation oxide film 2. A resistpattern 5ais formed on the region of first dopedpolysilicon film 3 positioned in the high Vdd region to be second gate electrode19 (seeFIG. 11 ). - Then, using resist
pattern 5aas a mask, a part of first dopedpolysilicon film 3 is anisotropically etched away to formsecond gate electrode 19. Thereafter, resistpattern 5ais removed. A resistpattern 5bis formed on secondgate insulating film 4 andisolation oxide film 2 positioned in the low Vdd region. An n type impurity is introduced into a prescribed region ofsemiconductor substrate 1 to form a low concentration, n typeimpurity diffusion region 16 as shown inFIG. 13 . The n type impurity used is phosphorus, the introduction energy is 20 keV, and the dose is 2×1013cm−2. The introduction energy may be in the range from 10 to 30 keV. Herein, sincesecond gate electrode 19 has been formed on secondgate insulating film 4, a resist pattern is not directly formed in the region of the surface of secondgate insulating film 4 in whichsecond gate electrode 19 is positioned, in the process of manufacturing which will be described. Defects in the region of the surface of secondgate insulating film 4 which are caused by a processing of removing the resist patterns or a light etching processing can be prevented. Resistpattern 5bis thereafter removed. - A
silicon nitride film 11 is formed on secondgate insulating film 4,second gate electrode 19 andisolation oxide film 2. Thus, the structure as shown inFIG. 14 results. Silicon nitride film 11 is then anisotropically etched to form sidewall nitride film21 (seeFIG. 11 ) which serves as an oxidation protection film to preventsecond gate electrode 19 from being oxidized on a sidewall ofsecond gate electrode 19. Resistpattern 5c(seeFIG. 15 ) is formed on secondgate insulating film 4,second gate electrode 19 andsidewall nitride film 21 to cover the high Vdd region to obtain the structure as shown inFIG. 15 .- Then, second
gate insulating film 4 present in the low Vdd region is isotropically etched to obtain the structure as shown inFIG. 16 . Resistpattern 5cis then removed away. - First
gate insulating film 6 is formed by means of thermal oxidation on the portion of the main surface ofsemiconductor substrate 1 positioned in the low Vdd region, on the surface of secondgate insulating film 4, and onsecond gate electrode 19. The structure as shown inFIG. 17 thus results. Herein, the thermal oxidation to form firstgate insulating film 6 may be performed after formingsidewall nitride film 21 serving as the oxidation protection film to preventsecond gate electrode 19 from being oxidized on a side ofsecond gate electrode 19. As a result, a lower part of a side ofsecond gate electrode 19 can be prevented from being oxidized, and a gate bird's beak can be prevented. - A second doped polysilicon film7 (see
FIG. 18 ) is formed to generally cover the entire surface. A resistpattern 5d(seeFIG. 18 ) is formed on the region of second dopedpolysilicon film 7 to be the first gate electrode (seeFIG. 11 ). Thus, the structure as shown inFIG. 18 results. - Then, using resist
pattern 5das a mask, a part of second dopedpolysilicon film 7 is anisotropically etched away to form first gate electrode18 (seeFIG. 11 ). Herein,silicon oxide film 6 formed by the thermal oxidation during forming firstgate insulating film 6 is present onsecond gate electrode 19. Therefore, during the anisotropic etching for formingfirst gate electrode 18,silicon oxide film 6 serves as a stopper, so that damages such as partial removal ofsecond gate electrode 19 by the anisotropic etching can be prevented. Thereafter, resistpattern 5d(seeFIG. 18 ) is removed. A resistpattern 5e(seeFIG. 19 ) is formed to generally cover the low Vdd region. Thus, the structure as shown inFIG. 19 results. At the time, second dopedpolysilicon film 7 also remains on a side ofsidewall nitride film 21. - Then, second doped
polysilicon film 7 on the side ofsidewall nitride film 21 is isotropically etched away. Then, resistpattern 5e(seeFIG. 19 ) is removed. An n type impurity is introduced into a prescribed region of the main surface ofsemiconductor substrate 1, and thus intermediate concentration, n typeimpurity diffusion regions FIG. 20 . The n type impurity is arsenic, the introduction energy is 60 keV, and the dose is 2×1013cm−2. The introduction energy may be in the range from 30 to 80 keV. Sidewall oxide films 9 and20 (seeFIG. 21 ) are then formed on a side offirst gate electrode 18 andsidewall nitride film 21. First and secondgate insulating films second gate electrodes sidewall oxide films sidewall nitride film 21 are etched away. An n type impurity is introduced into a prescribed region of the main surface of semiconductor substrate. As shown inFIG. 21 , high concentration, n typeimpurity diffusion regions - Thus, the 2-power supply semiconductor device including the plurality of field effect transistors according to the second embodiment is manufactured.
- Third Embodiment
- Referring to
FIG. 22 , in a 2-power supply semiconductor device including a plurality of field transistors according to a third embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10, and a pair ofimpurity diffusion regions 8, spaced apart from each other and having a first channel region. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity region 8 constitute an LDD structure. Anoxide nitride film 13 serving as a gate insulating film is formed on the first channel region. Afirst gate electrode 18 is formed onoxide nitride film 13. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10 andimpurity diffusion regions 8,oxide nitride film 13, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17, and a pair ofimpurity diffusion regions 16 spaced apart from each other and having a second channel therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the channel region. Asecond gate electrode 19 is formed on secondgate insulating film 4. Anoxide nitride film 13 is formed on a side ofsecond gate electrode 19 and on secondgate insulating film 4. Asidewall oxide film 20 is formed onoxide nitride film 13. Second source/drain regions 17, andimpurity diffusion regions 16, secondgate insulating film 4, andsecond gate electrode 19 form the second field effect transistor. Thus, thegate insulating film 13 of the first field effect transistor is formed of an oxide nitride film, an end ofsecond gate electrode 19 in the junction of a lower part of the side ofsecond gate electrode 19 and secondgate insulating film 4 can be prevented from being excessively oxidized. The generation of a gate bird's beak can be restricted. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. Furthermore, since the first gate insulating film is formed ofoxide nitride film 13, the driving capability of the transistor may be improved in terms of thickness as compared to a conventional silicon oxide film or the like. - Referring to
FIG. 23 , a first variation of the 2-power supply semiconductor device including the plurality of field effect transistors according to the third embodiment has basically the same structure as the 2-power supply semiconductor device according to the first embodiment shown inFIG. 1 . However, in the first variation shown inFIG. 23 , the firstgate insulating film 13 is formed of oxide nitride film. A second variation of the third embodiment shown inFIG. 24 has basically the same structure as the device according to the second embodiment shown inFIG. 11 . However, as shown inFIG. 24 , in the device according to the second variation, as is the case with the examples shown inFIGS. 22 and 23 , the firstgate insulating film 13 is formed of oxide nitride film. Therefore, the driving capability of the transistor may be improved as compared to the case of using the conventional silicon oxide film in terms of thickness in addition to the effects brought about according to the first and second embodiments. - Referring to FIGS.25 to32, a process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors shown in
FIG. 22 according to the third embodiment will be described. - The manufacturing process shown in
FIG. 25 is identical to the manufacturing process according to the first embodiment shown inFIG. 2 . - Now, a part of first doped
polysilicon film 3 is anisotropically etched away, using a resistpattern 5a(seeFIG. 25 ) as a mask, to form second gate electrode19 (seeFIG. 22 ), followed by removal of resistpattern 5a(seeFIG. 25 ). A resistpattern 5b(seeFIG. 26 ) is formed on secondgate insulating film 4 and onsecond gate electrode 19 to cover the high Vdd region, and the structure as shown inFIG. 26 results. Herein, resistpattern 5bis formed aftersecond gate electrode 19 is formed on secondgate insulating film 4, resistpattern 5bis not directly formed in the region of the surface of secondgate insulating film 4 in whichsecond gate electrode 19 is positioned. As a result, defects in the region of the surface of secondinsulating film 4 caused by a processing of removing resistpattern 5boralight etching processing can be prevented. - Second
gate insulating film 4 present in the low Vdd region is isotropically etched away to obtain the structure as shown inFIG. 27 . Thereafter, resistpattern 5bis removed. - Then,
oxide nitride film 13 to be the first gate insulating film is formed at the position of the main surface ofsemiconductor substrate 1 positioned in the low Vdd region, on the surface of secondgate insulating film 4, and onsecond gate electrode 19 by means of thermal oxidation using N2O or O2as a gas atmosphere. Thus, the structure as shown inFIG. 28 results. Herein,oxide nitride film 13 is formed as the first gate insulating film, an end ofsecond gate electrode 19 can be prevented from being excessively oxidized in the junction of a lower part of the side ofsecond gate electrode 19 and secondgate insulating film 4. Thus, a gate bird's beak can be prevented. Furthermore, sinceoxide nitride film 13 is formed as the first gate insulating film, the thickness ofoxide nitride film 13 as the first gate insulating film may be smaller than a conventional silicon oxide film, while maintaining a prescribed breakdown voltage. As a result, the driving voltage of the first field effect transistor can be reduced. - The manufacturing process as shown in FIGS.29 to32 is substantially identical to the manufacturing process according to the first embodiment shown in FIGS.7 to10.
- Thus, the 2-power supply semiconductor device according to the third embodiment as shown in
FIG. 22 is manufactured. - Fourth Embodiment
- Referring to
FIG. 33 , in a 2-power supply semiconductor device including a plurality of field transistors according to a fourth embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second power supply voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10, and a pair ofimpurity diffusion regions 8, spaced apart from each other and having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity region 8 constitute an LDD structure. A firstgate insulating film 6 is formed on the first channel region. Afirst gate electrode 18 is formed on firstinsulating film 6. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10,impurity regions 8, firstgate insulating film 6, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17 and a pair ofimpurity diffusion regions 16, spaced apart from each other and having a second channel therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the second channel region. A nitrogen dopedpolysilicon film 14 serving as an anti-oxidation conductive film is formed on secondgate insulating film 4. A first dopedpolysilicon film 13 doped with a p type or n type impurity is formed on nitrogen dopedpolysilicon film 14. Nitrogen dopedpolysilicon film 14 and first dopedpolysilicon film 3 form asecond gate electrode 19. Asidewall oxide film 20 is form on a side ofsecond gate electrode 19. Second source/drain regions 17,impurity diffusion regions 16, secondgate insulating film 4, andsecond gate electrode 19 form the second field effect transistor. Herein, the thickness of secondgate insulating film 4 of the second field effect transistor should be larger than the thickness of the firstgate insulating film 6 of the first field effect transistor in view of breakdown voltage. - As described above, since nitrogen doped
polysilicon film 14 serving as an anti-oxidation conductive film is formed on secondgate insulating film 4, it is not necessary to form a resist pattern directly on the surface of secondgate insulating film 4 in the following process of manufacturing. Furthermore, before formingsecond gate electrode 19, firstgate insulating film 6 is formed using nitrogen dopedpolysilicon film 14 as a mask, an oxidizing step may be performed while hardly oxidizing the surface of nitrogen dopedpolysilicon film 14. As a result, in the oxidizing step to form agate insulating film 6, a lower part of a side ofsecond gate electrode 19 is not oxidized, and a gate bird's beak can be prevented. Thus, the threshold voltage of the second field effect transistor can be prevented from increasing, and electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - In addition, since first and second
gate insulating films gate insulating films second gate electrodes - In addition, nitrogen doped
polysilicon film 14 is formed on secondgate insulating film 4, a resist pattern is not directly formed on secondgate insulating film 4. As a result, defects such as local irregularities in the gate insulating film as formed during removing a resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating. - Referring to FIGS.34 to37, a process of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment will be described.
Isolation oxide film 2 is formed to surround an active region on the main surface of ptype semiconductor substrate 1. Secondgate insulating film 4 is formed on the active region of the main surface ofsemiconductor substrate 1. Nitrogen dopedpolysilicon film 14 to be the anti-oxidation conductive film is formed on secondgate insulating film 4 andisolation oxide film 2. Resistpattern 5ais formed on nitrogen dopedpolysilicon film 14 positioned in the high Vdd region. Thus the structure as shown inFIG. 34 is obtained. Since nitrogen dopedpolysilicon film 14 is formed on secondgate insulating film 4 and resistpattern 5ais formed, resistpattern 5ais not directly formed on the surface of second gate insulating film. As a result, defects caused by a processing of removing resistpattern 5aoralight etching processing can be prevented on the surface of secondgate insulating film 4. As a result, the fluctuation of the threshold voltages of the field effect transistors can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from the deteriorating.- Nitrogen doped
polysilicon film 14 and secondgate insulating film 4 present in the low Vdd region are removed by means of isotropic etching, and the structure as shown inFIG. 35 results. Resistpattern 5ais thereafter removed. - As shown in
FIG. 36 , firstgate insulating film 6 is formed on the main surface ofsemiconductor substrate 1 positioned in the low Vdd region. At the time, the surface of nitrogen dopedpolysilicon film 14 is little oxidized, because its surface had nitrogen introduced. - First doped
polysilicon film 3 is formed on firstgate insulating film 6, nitrogen dopedpolysilicon film 14 andisolation oxide film 2. Resistpatterns polysilicon film 3 to be first andsecond gate electrodes 18 and19 (seeFIG. 33 ), and the structure as shown inFIG. 37 results. - Using resist
patterns polysilicon film 3 is anisotropically etched away to form first andsecond gate electrodes 18 and19 (seeFIG. 33 ). Since nitrogen dopedpolysilicon film 14 serving as the anti-oxidation conductive film is formed on secondgate insulating film 4, first andsecond gate electrodes gate insulating films first gate electrode 18 andsecond gate electrode 19 may be formed in a single anisotropic etching processing, the number of steps included in the manufacture of the semiconductor device may be reduced. Furthermore, since nitrogen dopedpolysilicon film 14 is formed on secondgate insulating film 4, nitrogen dopedpolysilicon film 14 serves as a barrier against an impurity when the impurity is introduced to form second source/drain regions 17 and impurity diffusion regions16 (seeFIG. 33 ). As a result, the impurity can be effectively prevented from being introduced into the second channel region. As a result, erroneous operations of the second field effect transistor caused by introduction of the impurity into the second channel region can be more effectively prevented. - Thereafter, an impurity is introduced into a prescribed region of the main surface of
semiconductor substrate 1, followed by formation ofsidewall oxide films 9 and20 (seeFIG. 33 ) on sides of first andsecond gate electrodes 18 and19 (seeFIG. 33 ), and the semiconductor device as shown inFIG. 33 is formed. - The 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment is thus manufactured.
- Referring to FIGS.38 to41, a process of manufacturing a 2-power supply semiconductor device including a plurality of field effect transistors according to a first variation of the fourth embodiment will be now described.
Isolation oxide film 2 is formed on the main surface of ptype semiconductor substrate 1 to surround an active region. An oxide film (not shown) is formed on the main surface ofsemiconductor substrate 1. A resist pattern (not shown) is formed on the oxide film positioned in the low Vdd region. Using the resist pattern as a mask, an impurity is introduced into the main surface ofsemiconductor substrate 1 positioned in the high Vdd region. Using the resist pattern as a mask, the oxide film positioned in the high Vdd region is isotropically etched away. Thereafter, the resist pattern is removed to form the structure as shown inFIG. 38 .- The manufacturing steps shown in
FIGS. 39 and 40 are substantially identical to the steps of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment. However, anoxide film 28 serving as a substrate protection film is formed on the main surface of semiconductor substrate positioned in the low Vdd region as shown inFIG. 39 . Thus, in the oxidizing step to form secondgate insulating film 4, the main surface ofsemiconductor substrate 1 positioned in the low Vdd region is not directly oxidized. Sinceoxide film 4 and nitrogen dopedpolysilicon film 14 are formed onoxide film 28, during isotropically etching away nitrogen dopedpolysilicon film 14 from the low Vdd region as shown inFIG. 40 ,oxide film 28 having a sufficient thickness can prevent the main surface ofsemiconductor substrate 1 positioned in the low Vdd region from being directly damaged by the isotropic etching. Thus, when first gate insulating film6 (seeFIG. 33 ) is formed in the low Vdd region, the deterioration of the quality of firstgate insulating film 6 because of possible damages by etching on the main surface ofsemiconductor substrate 1 can be prevented. As a result, the fluctuation of the threshold voltage of the first field effect transistor can be prevented. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - The manufacturing process according to the first variation of the fourth embodiment shown in
FIG. 41 is substantially identical to the manufacturing process according to the fourth embodiment shown inFIG. 37 . An impurity is thereafter introduced into a prescribed region of the main surface ofsemiconductor substrate 1, followed by formation ofsidewall oxide films 9 and20 (seeFIG. 33 ) on sides of first andsecond gate electrodes 18 and19 (seeFIG. 33 ), to form the semiconductor device as shown inFIG. 33 . - Referring to
FIGS. 42 and 43 , a process of manufacturing a 2-power supply semiconductor device including a plurality of field effect transistors according to a second variation of the fourth embodiment will be now described. - Among the steps of manufacturing the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment, after performing the steps shown in
FIGS. 34 and 35 , resistpattern 5a(seeFIG. 35 ) is removed. Then, the entire surface ofsemiconductor substrate 1 is oxidized to form anoxide film 29 on the main surface ofsemiconductor substrate 1 positioned in the low Vdd region to obtain the structure as shown inFIG. 42 . - Then, as shown in
FIG. 43 , oxide film29 (seeFIG. 42 ) is isotropically etched away. In the manufacturing process according to the second variation of the fourth embodiment, after the main surface ofsemiconductor substrate 1 positioned in the low Vdd region is oxidized, oxide film29 (seeFIG. 42 ) is thus isotropically etched away, possible damages generated by etching on the main surface positioned in the low Vdd region ofsemiconductor substrate 1 caused by an etching processing to remove oxide film4 (seeFIG. 34 ) and nitrogen doped polysilicon film14 (seeFIG. 34 ) from the main surface ofsemiconductor substrate 1 positioned in the low Vdd region can be removed by isotropically etching a part of the main surface ofsemiconductor substrate 1 with the defects. As a result, during forming first gate insulating film6 (seeFIG. 33 ), the deterioration of the quality of firstgate insulating film 6 because of damages by etching such as local irregularities on the surface ofsemiconductor substrate 1 may be prevented. As a result, the fluctuation of the threshold voltages of the field effect transistors may be prevented, and as a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - After the step shown in
FIG. 43 , the steps to manufacture the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment shown inFIGS. 36 and 37 are performed to obtain the semiconductor device as shown inFIG. 33 . - Referring to
FIG. 44 , a 2-power supply semiconductor device including a plurality of field effect transistors according to a third variation of the fourth embodiment of the invention has substantially the same structure as the 2-power supply semiconductor device according to the fourth embodiment shown inFIG. 33 . However, as shown inFIG. 44 , in the device according to the third variation, there is formed a dopedpolysilicon film 32 having a conductive impurity between secondgate insulating film 4 and nitrogen dopedpolysilicon film 14. Therefore, in the 2-power supply semiconductor device according the third variation, in addition to the effects brought about by the device according to the fourth embodiment, the formation of a depletion layer caused by a reduction in the density of the conductive impurity in the vicinity of secondgate insulating film 4 when a voltage is supplied togate electrode 19 can be restrained. As a result, the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layer can be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Referring to
FIGS. 45 and 46 , a process of manufacturing the 2-power supply semiconductor device according to the third variation of the fourth embodiment of the invention will be now described. - As shown in
FIG. 45 ,isolation oxide film 2 is formed to surround an active region on the main surface of ptype semiconductor substrate 1. Secondgate insulating film 4 is formed on the active region of the main surface ofsemiconductor substrate 1.Doped polysilicon film 32 having a conductive impurity is formed between secondgate insulating film 4 andisolation oxide film 2. Nitrogen dopedpolysilicon film 14 is formed on dopedpolysilicon film 32. - After performing the steps substantially identical to the manufacturing steps according to the fourth embodiment of the invention as shown in FIGS.34 to36, a
polysilicon film 7 is formed to generally cover the entire semiconductor device as shown inFIG. 46 . Resistpatterns polysilicon film 7. - Using resist
patterns polysilicon film 7, nitrogen dopedpolysilicon film 14 and dopedpolysilicon film 32 to form first andsecond gate electrodes 18 and19 (seeFIG. 44 ). - Thereafter, an impurity is introduced into a prescribed region of the main surface of
semiconductor substrate 1, followed by formation of a sidewall oxide film9 (seeFIG. 44 ) on sides of first andsecond gate electrodes 18 and19 (seeFIG. 44 ), and the semiconductor device as shown inFIG. 44 results. - In the 2-power supply semiconductor device including the plurality of field effect transistors according to the fourth embodiment, nitrogen doped
polysilicon film 14 is formed in the high Vdd region, the same effects can be brought about by forming nitrogen dopedpolysilicon film 14 in the low Vdd region. - Fifth Embodiment
- Referring to
FIG. 47 , In a 2-power supply semiconductor device including a plurality of field transistors according to a fifth embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10, and a pair ofimpurity diffusion regions 8 spaced apart from each other and having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity diffusion region 8 constitute an LDD structure. A firstgate insulating film 6 is formed on the first channel region. Afirst gate electrode 18 is formed on firstinsulating film 6. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10,impurity diffusions 8, firstgate insulating film 6, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17, and a pair ofimpurity diffusion regions 16, spaced apart from each other and having a second channel therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. Secondgate insulating film 4 is formed on the second channel region.Doped polysilicon film 32 having a conductive impurity is formed on secondgate insulating film 4. Anitride film 27 is formed on a dopedpolysilicon film 32. A dopedpolysilicon film 7 is formed onnitride film 27.Doped polysilicon film 32,nitride film 27 and dopedpolysilicon film 7 form asecond gate electrode 19. Asidewall oxide film 9 is formed on a side ofsecond gate electrode 19. Herein,nitride film 27 is formed by nitriding the surface of dopedpolysilicon film 32 by lamp annealing as in the manufacturing steps which will be described and is a tunnel insulating film through which a current may be passed when voltage is supplied togate electrode 19. Second source/drain regions 17,impurity diffusion regions 16, secondgate insulating film 4, andsecond gate electrode 19 form the second field effect transistor. - Thus, doped
polysilicon film 32 andnitride film 27 are formed on secondgate insulating film 4, it is not necessary to form a resist pattern directly on the surface of secondgate insulating film 4. An oxidizing step to form firstgate insulating film 6 may be performed, usingnitride film 27 as a mask before formingsecond gate electrode 19. As a result, a lower part of a side ofsecond gate electrode 19 is not oxidized in the step of oxidizing firstgate insulating film 6, and therefore a gate bird's beak can be prevented. Therefore, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Furthermore, since doped
polysilicon film 32 is formed on secondgate insulating film 4, a resist pattern is not formed directly on secondgate insulating film 4. Therefore, as a result, defects such as local irregularities in the gate insulating film as formed during removing the resist pattern can be avoided. Therefore, the threshold voltages of the field effect transistors may be prevented from fluctuating. Electrical characteristics of the semiconductor device including the plurality of field effect transistors may be prevented from deteriorating. - In addition, before forming
second gate electrode 19,gate insulating films second gate electrodes gate insulating films - Furthermore, since doped
polysilicon film 32 including a conductive impurity is formed on secondgate insulating film 4, when a voltage is supplied togate electrode 19, the formation of a depletion layer caused by a reduction in the density of the conductive impurity in the vicinity of secondgate insulating film 4 may be restricted. As a result, the fluctuation of the threshold voltages of the field effect transistors caused by the formation of such a depletion layer can be prevented. Therefore, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Referring to
FIG. 48 , a process of manufacturing the 2-power supply semiconductor device according to the fifth embodiment will be now described. - As shown in
FIG. 48 ,isolation oxide film 2 is formed to surround an active region on the main surface of ptype semiconductor substrate 1. Secondgate insulating film 4 is formed on the active region on the main surface ofsemiconductor substrate 1.Doped polysilicon film 32 including a conductive impurity is formed on secondgate insulating film 4 andisolation oxide film 2. The surface of dopedpolysilicon film 32 is nitrided by means of lamp annealing to formnitride film 27. - After the step shown in
FIG. 48 , the steps substantially the same as those shown in FIGS.34 to37 related to the 2-power supply semiconductor device according to the fourth embodiment are performed. Thus, semiconductor device as shown inFIG. 47 results. - In the step corresponding to the step shown in
FIG. 36 , dopedpolysilicon film 32 andnitride film 27 are formed on secondgate insulating film 4, a resist pattern does not have to be formed directly on the surface of secondgate insulating film 4. Furthermore, before formingsecond gate electrode 19, an oxidizing step to form firstgate insulating film 6 usingnitride film 27 as a mask may be performed. Thus, in the step of oxidizing firstgate insulating film 6, a lower part of a side ofsecond gate electrode 19 is not oxidized, and as a result, a gate bird's beak can be prevented. As a result, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Furthermore, since first and second
gate insulating films FIG. 37 , doped polysilicon film7 (seeFIG. 47 ) may be formed in the region positioned above first and secondgate insulating films second gate electrodes - Sixth Embodiment
- Referring to
FIG. 49 , in a 2-power supply semiconductor device including a plurality of field transistors according to a sixth embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10, and a pair ofimpurity diffusion regions 8 spaced apart from each other and having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity diffusion region 8 constitute an LDD structure. A firstgate insulating film 6 is formed on the first channel region. Afirst gate electrode 18 is formed on firstgate insulating film 6. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10,impurity diffusion regions 8, firstgate insulating film 6, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17, a pair ofimpurity diffusion regions 16 spaced apart from each other and having a second channel therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the second channel region. A first dopedpolysilicon film 3 is formed on secondgate insulating film 4. An insulatingfilm 6 of the same material as that of firstgate insulating film 6 is formed on first dopedpolysilicon film 3. A second dopedpolysilicon film 22 is formed on insulatingfilm 6. First dopedpolysilicon film 3, insulatingfilm 6, and second dopedpolysilicon film 22 formsecond gate electrode 19. Asidewall oxide film 20 is formed on a side ofsecond gate electrode 19. Second source/drain regions 17,impurity diffusion regions 16, secondgate insulating film 4, andsecond gate electrode 19 form the second field effect transistor. - Thus,
second gate electrode 19 is formed to have first dopedpolysilicon 3, insulatingfilm 6 in the high Vdd region and second dopedpolysilicon film 22, a resist pattern is not directly formed on the surface of secondgate insulating film 4 in the step of manufacture which will be described, an oxidizing step to form firstgate insulating film 6 in the low Vdd region may be performed before formingsecond electrode 19. As a result, a gate bird's beak caused by oxidation of a side ofsecond electrode 19 can be prevented. Furthermore, when high Vdd is supplied tosecond gate electrode 19, a voltage imposed on secondgate insulating film 4 can be reduced by a voltage drop at insulatingfilm 6 in the high Vdd region. - Assuming that the thickness of first
gate insulating film 6 in low Vdd region is t1, the thickness of second gate insulating film4 t2, the thickness of insulatingfilm 6 in the high Vdd region t3, a voltage supplied to first gate electrode18 V1, and a voltage supplied to second gate electrode19 V2, the thicknesses of insulatingfilm 6 in the high Vdd region, firstgate insulating film 6 in the low Vdd region and secondgate insulating film 4 may be adjusted such that t1/(t2+t3) is substantially equal to V1/V2, and the static characteristic of first and second field effect transistors can be adjusted to be substantially equal to each other. - Referring to FIGS.50 to55, a process of manufacturing the 2-power supply semiconductor device according to the fifth embodiment will be now described.
- As shown in
FIG. 50 ,isolation oxide film 2 is formed on the main surface of ptype semiconductor substrate 1 to surround an active region. Secondgate insulating film 4 is formed on the active region of the main surface ofsemiconductor substrate 1. First dopedpolysilicon film 3 is formed on secondgate insulating film 4 andisolation oxide film 2. Thereafter, a resistpattern 5ais formed on first dopedpolysilicon film 3 positioned in the high Vdd region. - First doped
polysilicon film 3 and secondgate insulating film 4 present in the low Vdd region are removed by isotropic etching. Thereafter, resistpattern 5ais removed. Thus, the structure as shown inFIG. 51 results. - First
gate insulating film 6 is formed on the portion of the main surface ofsemiconductor substrate 1 positioned in the low Vdd region and on first dopedpolysilicon film 3 by means of thermal oxidation. Thus, the structure as shown inFIG. 52 results. Before forming second gate electrode19 (seeFIG. 49 ), an oxidizing step to form firstgate insulating film 6 is performed, a gate bird's beak caused by oxidation of a side ofsecond gate electrode 19 can be prevented. Furthermore, since first dopedpolysilicon film 3 is formed on secondgate insulating film 4, a resist pattern is not directly formed onto the surface of secondgate insulating film 4. As a result, a processing of removing the resist pattern is not directly performed on the surface of secondgate insulating film 4, and defects on the surface of secondgate insulating film 4 can be prevented. - Then, second doped
polysilicon film 7 is formed on firstgate insulating film 6 andisolation oxide film 2. By forming resistpatterns polysilicon film 7 in the low Vdd region and on the region to be second gate electrode19 (seeFIG. 49 ), the structure as shown inFIG. 53 results. - Then, using resist
patterns polysilicon film 7, firstgate insulating film 6, and firstdoped polysilicon 3 to form second gate electrode19 (seeFIG. 49 ). Thereafter, resistpatterns FIG. 53 ) are removed. Resistpatterns insulating film 4,second gate electrode 19, and the region to be thegate electrode 18 of doped polysilicon film7 (seeFIG. 49 ). Thus, the structure as shown inFIG. 54 results. - Then, using resist
patterns polysilicon film 7 and thus first gate electrode18 (seeFIG. 49 ) is formed. Thereafter, resistpatterns FIG. 55 . Then, an impurity is introduced into a prescribed region of the main surface ofsemiconductor substrate 1, followed by formation ofsidewall oxide films 9 and20 (seeFIG. 49 ) on sides of first andsecond gate electrodes FIG. 49 . - Seventh Embodiment
- Referring to
FIG. 56 , in a 2-power supply semiconductor device including a plurality of field transistors according to a seventh embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10 and a pair ofimpurity diffusion regions 8, spaced apart from each other and having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity region 8 constitute an LDD structure. A firstgate insulating film 6 is formed on the first channel region. A dopedpolysilicon film 31 is formed on firstgate insulating film 6.Doped polysilicon film 31 has a relatively small thickness for example of about 500 Å. Anatural oxide film 30 is formed on dopedpolysilicon film 31. A dopedpolysilicon film 7 is formed onnatural oxide film 30.Doped polysilicon film 31,natural oxide film 30 and dopedpolysilicon film 7 formfirst gate electrode 18. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10 andimpurity diffusion regions 8, firstgate insulating film 6 andfirst gate electrode 18 form first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17, a pair ofimpurity diffusion regions 16, spaced apart from each other and having a second channel therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the second channel region. A dopedpolysilicon film 32 is formed on secondgate insulating film 4.Doped polysilicon film 32 has a relatively small thickness for example of about 500 Å.Natural oxide film 30 is formed on dopedpolysilicon film 32.Doped polysilicon film 7 is formed onnatural oxide film 30.Doped polysilicon film 32,natural oxide film 30 and dopedpolysilicon film 7 constitutesecond gate electrode 19. Asidewall oxide film 9 is formed on a side ofsecond gate electrode 19. Second source/drain regions 17,impurity diffusion regions 16, secondgate insulating film 4, andsecond gate electrode 19 form the second field effect transistor. - Thus,
doped polysilicon films gate insulating films gate insulating films gate insulating film 6 can be performed using dopedpolysilicon film 32 as a mask, before formingsecond gate electrode 19. Thus, in the step of oxidizinggate insulating film 6, as a result, a lower part of a side ofsecond gate electrode 19 can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Furthermore, by making
doped polysilicon films gate insulating films polysilicon films second gate electrodes second gate electrodes second gate electrodes first gate electrode 18 can be almost the same as the amount of etching to formsecond gate electrode 19. As a result, the amount of overetching in forming first andsecond gate electrodes semiconductor substrate 1 positioned under dopedpolysilicon films - Furthermore, since doped
polysilicon films gate insulating films gate insulating films gate insulating films - Referring to FIGS.57 to60, a method of manufacturing the 2-power supply semiconductor device according to the seventh embodiment of the invention will be described.
- As shown in
FIG. 57 ,isolation oxide film 2 to surround an active region is formed on the main surface of ptype semiconductor substrate 1. Secondgate insulating film 4 is formed on the active region of the main surface ofsemiconductor substrate 1.Doped polysilicon film 32 is formed on secondgate insulating film 4 andisolation oxide film 2. Thereafter, a resistpattern 5fis then formed on dopedpolysilicon film 32 positioned in the high Vdd region. - Using resist
pattern 5fas a mask, secondgate insulating film 4 and dopedpolysilicon film 32 positioned in the low Vdd region are etched away, followed by removal of resistpattern 5f. Since dopedpolysilicon film 32 is formed on secondgate insulating film 4, resistpattern 5fis not directly formed on secondgate insulating film 4. As a result, defects such as fine irregularities in the surface of secondgate insulating film 4 caused by the removal of resistpattern 5fcan be prevented. - As shown in
FIG. 58 , firstgate insulating film 6 is formed on the main surface ofsemiconductor substrate 1 positioned in the low Vdd region and on dopedpolysilicon film 32.Doped polysilicon film 31 is then formed on first gate insulating film andisolation oxide film 2. A resistpattern 5iis formed on dopedpolysilicon film 31 in the low Vdd region. - Since doped
polysilicon film 32 is formed on secondgate insulating film 4, an oxidizing step to form firstgate insulating film 6 can be performed using dopedpolysilicon film 32 as a mask before forming second gate electrode19 (seeFIG. 56 ). Thus, in the step of oxidizinggate insulating film 6, a lower part of a side ofsecond gate electrode 19 can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Furthermore, by making
doped polysilicon films second electrodes 18 and19 (seeFIG. 56 ), the amount of etching to formfirst gate electrode 18 can be substantially the same as the amount of etching to formsecond gate electrode 19. As a result, the amount of overetching during forming first andsecond gate electrodes - Then,
doped polysilicon film 31 andgate insulating film 6 positioned in the high Vdd region are etched away, using resistpattern 5ias a mask, followed by removal of resistpattern 5i. Thus, the structure as shown inFIG. 59 results. Herein,polysilicon films semiconductor substrate 1 andisolation oxide film 2. Thus, in the manufacture of the semiconductor device, there is no such region having a thickness as large as the sum of the thicknesses of dopedpolysilicon films gate electrodes - A part of the surfaces of first and second
doped polysilicon films polysilicon film 7 having for example a thickness of about 1500 Å is formed on the entire surface ofsemiconductor substrate 1. At the time,natural oxide film 30 has been formed on the surfaces of dopedpolysilicon films patterns polysilicon film 7. Thus, the structure as shown inFIG. 60 results. - Thereafter, using resist
patterns polysilicon films natural oxide film 30 is etched away to form first andsecond gate electrodes 18 and19 (seeFIG. 56 ). An impurity is introduced into a prescribed region of the main surface ofsemiconductor substrate 1, followed by formation of a sidewall oxide film9 (seeFIG. 56 ) on sides of first andsecond gate electrodes FIG. 56 results. Herein, if the thickness of dopedpolysilicon films second gate electrodes polysilicon films natural oxide film 30, and damages by the etching are not caused on first and secondgate insulating films polysilicon films semiconductor substrate 1. As a result, during etching to form first andsecond gate electrodes natural oxide film 30 can be readily performed, and the etching margin can be improved as compared to the case of removingnatural oxide film 30 by etching the doped polysilicon films. - Referring to
FIG. 61 , a 2-power supply semiconductor device including a plurality of field effect transistors according to a first variation of the seventh embodiment has basically the same structure as the 2-power supply semiconductor device according to the seventh embodiment shown inFIG. 56 with difference being thatsilicon films gate insulating films silicon films gate insulating films etching silicon films silicon films gate insulating films polysilicon film 32 having a large number of crystals as shown inFIG. 62 where the isotropic etching agent runs along grain boundaries to reachgate insulating film 4. Meanwhile, as shown inFIG. 63 , in the case ofsilicon film 34, having an amorphous structure which is free from grain boundaries, the isotropic etching agent does not run along grain boundaries to reachgate insulating film 4. - Therefore, damages caused by the isotropic etching agent can be prevented in
gate insulating films 4, and the fluctuation of the threshold voltages of field effect transistors caused by such damages in the gate insulating film can be prevented. As a result, electrical characteristics of the 2-power supply semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Referring to
FIG. 64 , a 2-power supply semiconductor device including a plurality of field effect transistors according to a second variation of the seventh embodiment has basically the same structure as the 2-power supply semiconductor device according to the seventh embodiment shown inFIG. 56 , with different being that thefirst gate electrode 31ais formed only of doped polysilicon film as shown inFIG. 64 , and that thesecond gate electrode 32ais formed only of doped polysilicon film. Since the first andsecond gate electrodes FIG. 56 ) in the 2-power supply semiconductor device according to the seventh embodiment can be omitted. Thus, the manufacturing process can be simplified as compared to the 2-power supply semiconductor device according to the seventh embodiment. - Referring to FIGS.65 to70, a method of manufacturing the 2-power supply semiconductor device according to the second variation of the seventh embodiment will be now described.
- As shown in
FIG. 65 ,isolation oxide film 2 is formed to surround an active region on the main surface of p type semiconductor substrate. Secondgate insulating film 4 is formed on the active region of the main surface ofsemiconductor substrate 1.Doped polysilicon film 32 is formed on secondgate insulating film 4 andisolation oxide film 2. A resistpattern 5fis formed on dopedpolysilicon film 32 positioned in the high Vdd region. - Using resist
pattern 5fas a mask, part of dopedpolysilicon film 32 and secondgate insulating film 4 is removed, followed by removal of resistpattern 5f. The structure as shown inFIG. 66 thus results. Herein, the thickness of dopedpolysilicon film 32 has such a thickness to be used as a gate electrode. - First gate insulating film6 (see
FIG. 67 ) is formed on the main surface ofsemiconductor substrate 1 and on dopedpolysilicon film 32. Doped polysilicon film31 (seeFIG. 67 ) is formed on firstgate insulating film 6. A resistpattern 5j(seeFIG. 67 ) is formed in the portion positioned in the low Vdd region on dopedpolysilicon film 31. Thus, the structure as shown inFIG. 67 results. - Since doped
polysilicon film 32 is formed on secondgate insulating film 4, an oxidizing step to form firstgate insulating film 6 may be performed using dopedpolysilicon film 32 as a mask before formingsecond gate electrode 32a(seeFIG. 64 ). Thus, in the step of oxidizinggate insulating film 6, as a result, a lower part of a side ofsecond gate electrode 32acan be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. Doped polysilicon film 31 and firstgate insulating film 6 positioned in the high Vdd region are etched away, using resistpattern 5jas a mask, followed by removal of resistpattern 5j, and the structure as shown inFIG. 68 thus results.- Then, as shown in
FIG. 69 , resistpatterns polysilicon films - As shown in
FIG. 70 , using resistpatterns FIG. 69 ) as masks, part of dopedpolysilicon films 31 and32 (seeFIG. 69 ) is anisotropically etched away to form first andsecond gate electrodes second gate electrodes polysilicon films 31 and32 (seeFIG. 69 ) serving as a protection conductive film, the number of steps for forming the doped polysilicon films can be reduced as compared to the process of manufacturing the 2-power supply semiconductor device according to the seventh embodiment shown in FIGS.57 to60. - An impurity is then introduced into a prescribed region of the main surface of
semiconductor substrate 1 followed by formation of a sidewall oxide film9 (seeFIG. 64 ) on sides of first andsecond gate electrodes FIG. 64 ), and the semiconductor device as shown inFIG. 64 results. - As an application of the second variation of the fourth embodiment, after oxidizing the main surface of
semiconductor substrate 1 positioned in the low Vdd region before forming firstgate insulating film 6, a part of the surface is isotropically etched to prevent the quality ofgate insulating film 6 from deteriorating. In addition, as applications of the first to third embodiment,doped polysilicon films gate insulating films - Eighth Embodiment
- Referring to
FIG. 71 in a 2-power supply semiconductor device including a plurality of field effect transistors according to an eighth embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistors supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10, a pair ofimpurity diffusion regions 8, spaced apart from each other and having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration n typeimpurity diffusion region 10 formed adjacent to n typeimpurity diffusion region 8 constitute an LDD structure. A firstgate insulating film 6 is formed on the first channel region. A dopedpolysilicon film 31 is formed on firstgate insulating film 6. Anitride film 27 is formed on dopedpolysilicon film 31. A dopedpolysilicon film 7 is formed onnitride film 27.Doped polysilicon films nitride film 27 form afirst gate electrode 18. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. The first source/drain regions 10,impurity diffusion regions 8, firstgate insulating film 6, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17, and a pair ofimpurity diffusion regions 16, spaced apart from each other and having a second channel region therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the second channel region. A dopedpolysilicon film 32 is formed on secondgate insulating film 4.Nitride film 27 is formed on dopedpolysilicon film 32.Doped polysilicon films nitride film 27 formsecond gate electrode 19.Sidewall oxide film 9 is formed on a side ofsecond gate electrode 19. Second source/drain regions 17,impurity diffusion regions 16, secondgate insulating film 4 andsecond gate electrode 19 form the second field effect transistor. - Since doped
polysilicon film 32 is formed on secondgate insulating film 4, an oxidizing step to form firstgate insulating film 6, using dopedpolysilicon film 32 as a mask can be performed before formingsecond gate electrode 19. As a result, in the step of oxidizinggate insulating film 6, a lower part of a side ofsecond gate electrode 19 can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Furthermore,
nitride film 27 is formed on dopedpolysilicon films polysilicon films polysilicon films second gate electrodes semiconductor substrate 1 positioned under dopedpolysilicon films - Referring to
FIG. 72 , a method of manufacturing the 2-power supply semiconductor device according to the eighth embodiment of the invention will be described. - After performing the steps in the manufacture of the 2-power supply semiconductor device according to the seventh embodiment shown in FIGS.57 to59, doped
polysilicon films FIG. 72 , andnitride film 27 serving as an oxidation protection film is formed. Herein,doped polysilicon film 32 is formed on secondgate insulating film 4, and therefore an oxidizing step to form firstgate insulating film 6 can be performed using dopedpolysilicon film 32 as a mask before formingsecond gate electrode 19. Thus, in the step of oxidizinggate insulating film 6, a lower part of a side ofsecond gate electrode 19 can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - Since
nitride film 27 is formed on the surfaces of dopedpolysilicon films polysilicon films polysilicon films second gate electrodes semiconductor substrate 1 positioned under dopedpolysilicon films - As is the case with the 2-power supply semiconductor device according to the seventh embodiment shown in
FIG. 60 , dopedpolysilicon film 7 is formed in the low Vdd region and the high Vdd region. Resist patterns are thereafter formed on dopedpolysilicon film 7, anisotropic etching is performed using the resist patterns as a mask to form first andsecond gate electrodes 18 and19 (seeFIG. 71 ). An impurity is introduced into the main surface ofsemiconductor substrate 1, followed by formation of a sidewall oxide film9 (seeFIG. 71 ) on sides of first andsecond gate electrodes FIG. 71 is thus obtained. - Ninth Embodiment
- Referring to
FIG. 73 , In a 2-power supply semiconductor device including a plurality of field transistors according to a ninth embodiment of the invention, there are formed, on a main surface of a ptype semiconductor substrate 1, a first field effect transistor supplied with a first power supply voltage (low Vdd) and a second field effect transistor supplied with a second voltage (high Vdd) higher than the first power supply voltage, spaced apart from each other. Anisolation oxide film 2 is formed between the first and second field effect transistors. - In the low Vdd region, there are formed, on the main surface of
substrate 1, a pair of first source/drain regions 10, and a pair ofimpurity diffusion regions 8, spaced apart from each other and having a first channel region therebetween. Low concentration, n typeimpurity diffusion region 8 formed adjacent to the first channel region and high concentration, n typeimpurity diffusion region 10 formed adjacent to n typeimpurity region 8 constitute an LDD structure. A firstgate insulating film 25 is formed on the first channel region. Afirst gate electrode 18 is formed on first insulatingfilm 25. Asidewall oxide film 9 is formed on a side offirst gate electrode 18. First source/drain regions 10,impurity diffusion regions 8, firstgate insulating film 25, andfirst gate electrode 18 form the first field effect transistor. - In the high Vdd region, there are formed, on the main surface of
semiconductor substrate 1, a pair of second source/drain regions 17, and a pair ofimpurity diffusion regions 16, spaced apart from each other and having a second channel therebetween. Low concentration, n typeimpurity diffusion region 16 formed adjacent to the second channel region and high concentration, n typeimpurity diffusion region 17 formed adjacent to n typeimpurity diffusion region 16 constitute an LDD structure. A secondgate insulating film 4 is formed on the second channel region. Asecond gate electrode 19 is formed on secondgate insulating film 4.Sidewall oxide film 9 is formed on a side ofsecond gate electrode 19. Second source/drain regions 17,impurity diffusion regions 16, secondgate insulating film 4 andsecond gate electrode 19 form the second field effect transistor. - Herein, in the 2-power supply semiconductor device according to the ninth embodiment, as will be described in connection with the following manufacturing steps, among first and second
gate insulating films gate insulating film 25 is isotropically etched to be reduced in thickness. Therefore, firstgate insulating film 25 can be formed before formingsecond gate electrode 19. As a result, a lower part of a side ofsecond gate electrode 19 can be prevented from being oxidized in the step of oxidizing to form firstgate insulating film 25, and a gate bird's beak caused by the oxidation can be prevented. Therefore, the threshold voltages of the field effect transistors can be prevented from increasing. - Referring to FIGS.74 to78, a method of manufacturing the 2-power supply semiconductor device according to the ninth embodiment will be now described.
- As shown in
FIG. 74 ,isolation oxide film 2 is formed to surround an active region on the main surface of ptype semiconductor substrate 1. Secondgate insulating film 4 is formed on the active region of the main surface ofsemiconductor substrate 1. A resistpattern 5fis formed on secondgate insulating film 4 andisolation oxide film 2, positioned in the high Vdd region. - Using resist
pattern 5fas a mask, a part of the surface of secondgate insulating film 4 positioned in the low Vdd region is isotropically etched away to form first gate insulating film25 (seeFIG. 75 ) thinner than secondgate insulating film 4 positioned in the high Vdd region. First and secondgate insulating films gate insulating film 4 and firstgate insulating film 25 in thickness is set substantially identical to the final difference in thickness between the first and second gate insulating films used in the field effect transistors. Resistpattern 5fis then removed to obtain the structure as shown inFIG. 75 . - At the time, the surface of second
gate insulating film 4 positioned in the high Vdd region may suffer from defects such as local irregularities caused by the process of removing the resist pattern. The surfaces of first and secondgate insulating films gate insulating films - Since first and second
gate insulating films gate insulating films pattern 5f(seeFIG. 74 ) present on the surface of secondgate insulating films 4 can be removed by the isotropic etching process. As a result, the first and secondgate insulating films - As shown in
FIG. 76 , a dopedpolysilicon film 3 is then formed on first and secondgate insulating films isolation oxide film 2. Resistpatterns polysilicon film 3. - Using resist
patterns polysilicon film 3 is anisotropically etched away to form first andsecond gate electrodes 18 and19 (seeFIG. 77 ), followed by removal of resistpatterns FIG. 77 , an impurity is then introduced into the main surface ofsemiconductor substrate 1, using first andsecond gate electrodes impurity diffusion regions semiconductor substrate 1. - Herein, the oxidizing step to form first and second
gate insulating films second gate electrode 19, a lower part of a side of the gate electrode can be prevented from being oxidized, and a gate bird's beak can be avoided. Thus, the threshold voltages of the field effect transistors can be prevented from increasing. As a result, electrical characteristics of the semiconductor device including the plurality of field effect transistors can be prevented from deteriorating. - A
sidewall oxide film 9 is then formed on sides of first andsecond gate electrodes FIG. 78 . Using first andsecond gate electrodes sidewall oxide film 9 as masks, impurity ions are introduced into the main surface ofsemiconductor substrate 11 to form high concentration, n typeimpurity diffusion regions FIG. 73 is thus obtained. - Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
Claims (10)
1-2. (Cancelled).
3. A semiconductor device including a plurality of field effect transistors including a first field effect transistor and a second field effect transistor,
said first field effect transistor including,
a pair of first source/drain regions formed on a main surface of a semiconductor substrate, spaced apart from each other and having a first channel region therebetween,
a first gate insulating film formed on said first channel region and having a first thickness, and
a first gate electrode formed on said first gate insulating film,
said second field effect transistor including,
a pair of second source/drain regions formed on the main surface of said semiconductor substrate, spaced apart from each other and having a second channel region therebetween, a second gate insulating film formed on said second channel region and having a second thickness larger than said first thickness, and
a second gate electrode formed on said second gate insulating film,
an anti-oxidation conductive film being formed on at least one of said first and second gate insulating films.
4. The semiconductor device as recited inclaim 3 , further comprising a semiconductor film having a conductive impurity and formed at a position between said anti-oxidation conductive film and at least one of said first and second gate insulating films.
5. A semiconductor device including a plurality of field effect transistors including a first field effect transistor and a second field effect transistor,
said first field effect transistor including,
a pair of first source/drain regions formed on a main surface of a semiconductor substrate, spaced apart from each other and having a channel region therebetween,
a first gate insulating film formed on said first channel region and having a first thickness, and
a first gate electrode formed on said first gate insulating film,
said second field effect transistor including,
a pair of second source/drain regions formed on the main surface of said semiconductor substrate, spaced apart from each other and having a second channel region therebetween,
a second gate insulating film formed on said second channel region and having a second thickness larger than said first thickness, and
a second gate electrode formed on said second gate insulating film,
a protection conductive film being formed on and in contact with at least one of said first and second gate insulating films.
6. The semiconductor device as recited inclaim 5 , further comprising an anti-oxidation insulation film for preventing said protection conductive film from being oxidized being formed on said protection conductive film.
7. The semiconductor device as recited inclaim 5 , wherein
one of said first and second gate electrodes have said protection conductive film as a first conductive film,
an insulating film formed on said first conductive film, and a second conductive film formed on said insulating film.
8. The semiconductor device as recited inclaim 5 , wherein
said protection conductive film includes first and second protection conductive films,
said first protection conductive film is formed on and in contact with said first gate insulating film, and
said second protection conductive film is formed on and in contact with said second gate insulating film,
said first protection conductive film and second protection conductive film are substantially identical in thickness.
9. The semiconductor device as recited inclaim 5 , wherein
said protection conductive film is formed by depositing a film having an amorphous structure.
10. The semiconductor device as recited inclaim 5 , further comprising an anti-oxidation film formed on and in contact with said protection conductive film.
11-17. (Cancelled)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/981,537US20050062099A1 (en) | 1997-06-09 | 2004-11-05 | Semiconductor device including multiple field effect transistors, with first fets having oxide spacers and the second fets having oxide nitride oxidation protection |
Applications Claiming Priority (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15094297 | 1997-06-09 | ||
| JP9-150942 | 1997-06-09 | ||
| JP9-244245 | 1997-09-09 | ||
| JP9244245AJPH1167927A (en) | 1997-06-09 | 1997-09-09 | Semiconductor device and manufacturing method thereof |
| US09/038,020US6541823B1 (en) | 1997-06-09 | 1998-03-11 | Semiconductor device including multiple field effect transistors and manufacturing method thereof |
| US10/370,762US6853030B2 (en) | 1997-06-09 | 2003-02-24 | Semiconductor device including multiple field effect transistors, with first FETs having oxide spacers and the second FETs having oxide nitride oxidation protection |
| US10/981,537US20050062099A1 (en) | 1997-06-09 | 2004-11-05 | Semiconductor device including multiple field effect transistors, with first fets having oxide spacers and the second fets having oxide nitride oxidation protection |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US10/370,762DivisionUS6853030B2 (en) | 1997-06-09 | 2003-02-24 | Semiconductor device including multiple field effect transistors, with first FETs having oxide spacers and the second FETs having oxide nitride oxidation protection |
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| Publication Number | Publication Date |
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| US20050062099A1true US20050062099A1 (en) | 2005-03-24 |
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| US09/038,020Expired - Fee RelatedUS6541823B1 (en) | 1997-06-09 | 1998-03-11 | Semiconductor device including multiple field effect transistors and manufacturing method thereof |
| US10/370,762Expired - Fee RelatedUS6853030B2 (en) | 1997-06-09 | 2003-02-24 | Semiconductor device including multiple field effect transistors, with first FETs having oxide spacers and the second FETs having oxide nitride oxidation protection |
| US10/981,537AbandonedUS20050062099A1 (en) | 1997-06-09 | 2004-11-05 | Semiconductor device including multiple field effect transistors, with first fets having oxide spacers and the second fets having oxide nitride oxidation protection |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US09/038,020Expired - Fee RelatedUS6541823B1 (en) | 1997-06-09 | 1998-03-11 | Semiconductor device including multiple field effect transistors and manufacturing method thereof |
| US10/370,762Expired - Fee RelatedUS6853030B2 (en) | 1997-06-09 | 2003-02-24 | Semiconductor device including multiple field effect transistors, with first FETs having oxide spacers and the second FETs having oxide nitride oxidation protection |
Country Status (4)
| Country | Link |
|---|---|
| US (3) | US6541823B1 (en) |
| JP (1) | JPH1167927A (en) |
| KR (1) | KR100335579B1 (en) |
| TW (1) | TW405252B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040238896A1 (en)* | 2003-06-02 | 2004-12-02 | Marie Mochizuki | Semiconductor device |
| US20110198696A1 (en)* | 2010-02-18 | 2011-08-18 | Globalfoundries Inc. | Finned semiconductor device with oxygen diffusion barrier regions, and related fabrication methods |
| US8497170B2 (en) | 2010-11-17 | 2013-07-30 | Fujitsu Semiconductor Limited | Semiconductor device manufacture method and semiconductor device |
| CN106461074A (en)* | 2014-04-28 | 2017-02-22 | 双环公司 | Trimmed lock-up clutch |
| TWI662620B (en)* | 2015-12-15 | 2019-06-11 | 台灣積體電路製造股份有限公司 | Semiconductor device structure and method for forming the same |
Families Citing this family (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6191017B1 (en)* | 1999-04-22 | 2001-02-20 | Lucent Technologies, Inc. | Method of forming a multi-layered dual-polysilicon structure |
| TW557569B (en)* | 2000-01-24 | 2003-10-11 | Sony Corp | Semiconductor device and manufacturing method thereof |
| US20020123180A1 (en)* | 2001-03-01 | 2002-09-05 | Peter Rabkin | Transistor and memory cell with ultra-short gate feature and method of fabricating the same |
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| JP4406540B2 (en)* | 2003-03-28 | 2010-01-27 | シャープ株式会社 | Thin film transistor substrate and manufacturing method thereof |
| US6943077B2 (en)* | 2003-04-07 | 2005-09-13 | Taiwan Semiconductor Manufacturing Co., Ltd. | Selective spacer layer deposition method for forming spacers with different widths |
| US7157341B2 (en)* | 2004-10-01 | 2007-01-02 | International Business Machines Corporation | Gate stacks |
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| JP4551795B2 (en)* | 2005-03-15 | 2010-09-29 | Ｏｋｉセミコンダクタ株式会社 | Manufacturing method of semiconductor device |
| JP4718894B2 (en)* | 2005-05-19 | 2011-07-06 | 株式会社東芝 | Manufacturing method of semiconductor device |
| US20060270127A1 (en)* | 2005-05-24 | 2006-11-30 | Taiwan Semiconductor Manufacturing Co., Ltd. | Method of forming dual gate variable VT device |
| DE102005046403A1 (en)* | 2005-09-28 | 2007-04-05 | Infineon Technologies Ag | Production of an integrated semiconductor circuit arrangement comprises forming a semiconductor circuit with first type field effect transistors and forming lateral edge regions to protect the gate insulation below the gate electrodes |
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| JP4714065B2 (en)* | 2006-03-31 | 2011-06-29 | Ｏｋｉセミコンダクタ株式会社 | Manufacturing method of semiconductor device |
| DE102008030856B4 (en)* | 2008-06-30 | 2015-12-03 | Advanced Micro Devices, Inc. | Threshold adjustment method for MOS devices |
| JP5435720B2 (en)* | 2009-12-21 | 2014-03-05 | パナソニック株式会社 | Semiconductor device |
| US9111935B2 (en) | 2013-03-12 | 2015-08-18 | International Business Machines Corporation | Multiple-patterned semiconductor device channels |
| US9099471B2 (en) | 2013-03-12 | 2015-08-04 | International Business Machines Corporation | Semiconductor device channels |
| US9076848B2 (en)* | 2013-03-12 | 2015-07-07 | International Business Machines Corporation | Semiconductor device channels |
| US20140353729A1 (en)* | 2013-05-29 | 2014-12-04 | United Microelectronics Corp. | Semiconductor structure and method for forming the same |
| KR102560699B1 (en)* | 2017-10-30 | 2023-07-27 | 삼성전자주식회사 | Image Sensor |
Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5502009A (en)* | 1995-02-16 | 1996-03-26 | United Microelectronics Corp. | Method for fabricating gate oxide layers of different thicknesses |
| US5567638A (en)* | 1995-06-14 | 1996-10-22 | National Science Council | Method for suppressing boron penetration in PMOS with nitridized polysilicon gate |
| US5719425A (en)* | 1996-01-31 | 1998-02-17 | Micron Technology, Inc. | Multiple implant lightly doped drain (MILDD) field effect transistor |
| US5721167A (en)* | 1997-02-10 | 1998-02-24 | Motorola, Inc. | Process for forming a semiconductor device and a static-random-access memory cell |
| US5736446A (en)* | 1997-05-21 | 1998-04-07 | Powerchip Semiconductor Corp. | Method of fabricating a MOS device having a gate-side air-gap structure |
| US5739589A (en)* | 1989-03-20 | 1998-04-14 | Hitachi, Ltd. | Semiconductor integrated circuit device process for fabricating the same and apparatus for fabricating the same |
| US5824588A (en)* | 1996-06-27 | 1998-10-20 | Winbond Electronics Corp. | Double spacer salicide MOS process and device |
| US5834352A (en)* | 1995-08-28 | 1998-11-10 | Samsung Electronics Co., Ltd. | Methods of forming integrated circuits containing high and low voltage field effect transistors therein |
| US5885877A (en)* | 1997-04-21 | 1999-03-23 | Advanced Micro Devices, Inc. | Composite gate electrode incorporating dopant diffusion-retarding barrier layer adjacent to underlying gate dielectric |
| US5908312A (en)* | 1996-05-07 | 1999-06-01 | Lucent Technologies, Inc. | Semiconductor device fabrication |
| US5987487A (en)* | 1996-03-11 | 1999-11-16 | Cirrus Logic, Inc. | Methods and apparatus for the processing of digital signals |
| US6015997A (en)* | 1997-02-19 | 2000-01-18 | Micron Technology, Inc. | Semiconductor structure having a doped conductive layer |
| US6578597B2 (en)* | 2001-03-08 | 2003-06-17 | Stant Manufacturing Inc. | Fuel tank vent system with liquid fuel filter |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63252459A (en) | 1987-04-09 | 1988-10-19 | Seiko Epson Corp | semiconductor equipment |
| JPH01110761A (en) | 1987-10-23 | 1989-04-27 | Nec Corp | Manufacture of semiconductor device |
| JP3189284B2 (en) | 1991-02-14 | 2001-07-16 | ソニー株式会社 | Method for manufacturing semiconductor device |
| JPH05267595A (en) | 1992-03-19 | 1993-10-15 | Fujitsu Ltd | Method for manufacturing semiconductor device |
- 1997
- 1997-09-09JPJP9244245Apatent/JPH1167927A/enactivePending
- 1998
- 1998-02-27TWTW087102836Apatent/TW405252B/ennot_activeIP Right Cessation
- 1998-03-11USUS09/038,020patent/US6541823B1/ennot_activeExpired - Fee Related
- 1998-05-11KRKR1019980016706Apatent/KR100335579B1/ennot_activeExpired - Fee Related
- 2003
- 2003-02-24USUS10/370,762patent/US6853030B2/ennot_activeExpired - Fee Related
- 2004
- 2004-11-05USUS10/981,537patent/US20050062099A1/ennot_activeAbandoned
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5739589A (en)* | 1989-03-20 | 1998-04-14 | Hitachi, Ltd. | Semiconductor integrated circuit device process for fabricating the same and apparatus for fabricating the same |
| US5502009A (en)* | 1995-02-16 | 1996-03-26 | United Microelectronics Corp. | Method for fabricating gate oxide layers of different thicknesses |
| US5567638A (en)* | 1995-06-14 | 1996-10-22 | National Science Council | Method for suppressing boron penetration in PMOS with nitridized polysilicon gate |
| US5834352A (en)* | 1995-08-28 | 1998-11-10 | Samsung Electronics Co., Ltd. | Methods of forming integrated circuits containing high and low voltage field effect transistors therein |
| US5719425A (en)* | 1996-01-31 | 1998-02-17 | Micron Technology, Inc. | Multiple implant lightly doped drain (MILDD) field effect transistor |
| US5987487A (en)* | 1996-03-11 | 1999-11-16 | Cirrus Logic, Inc. | Methods and apparatus for the processing of digital signals |
| US5908312A (en)* | 1996-05-07 | 1999-06-01 | Lucent Technologies, Inc. | Semiconductor device fabrication |
| US5824588A (en)* | 1996-06-27 | 1998-10-20 | Winbond Electronics Corp. | Double spacer salicide MOS process and device |
| US5721167A (en)* | 1997-02-10 | 1998-02-24 | Motorola, Inc. | Process for forming a semiconductor device and a static-random-access memory cell |
| US6015997A (en)* | 1997-02-19 | 2000-01-18 | Micron Technology, Inc. | Semiconductor structure having a doped conductive layer |
| US5885877A (en)* | 1997-04-21 | 1999-03-23 | Advanced Micro Devices, Inc. | Composite gate electrode incorporating dopant diffusion-retarding barrier layer adjacent to underlying gate dielectric |
| US5736446A (en)* | 1997-05-21 | 1998-04-07 | Powerchip Semiconductor Corp. | Method of fabricating a MOS device having a gate-side air-gap structure |
| US6578597B2 (en)* | 2001-03-08 | 2003-06-17 | Stant Manufacturing Inc. | Fuel tank vent system with liquid fuel filter |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040238896A1 (en)* | 2003-06-02 | 2004-12-02 | Marie Mochizuki | Semiconductor device |
| US20070173009A1 (en)* | 2003-06-02 | 2007-07-26 | Marie Mochizuki | Method of fabricating a dual-gate structure that prevents cut-through and lowered mobility |
| US7566604B2 (en) | 2003-06-02 | 2009-07-28 | Oki Semiconductor Co., Ltd. | Method of fabricating a dual-gate structure that prevents cut-through and lowered mobility |
| US20110198696A1 (en)* | 2010-02-18 | 2011-08-18 | Globalfoundries Inc. | Finned semiconductor device with oxygen diffusion barrier regions, and related fabrication methods |
| US8354719B2 (en)* | 2010-02-18 | 2013-01-15 | GlobalFoundries, Inc. | Finned semiconductor device with oxygen diffusion barrier regions, and related fabrication methods |
| US8497170B2 (en) | 2010-11-17 | 2013-07-30 | Fujitsu Semiconductor Limited | Semiconductor device manufacture method and semiconductor device |
| CN106461074A (en)* | 2014-04-28 | 2017-02-22 | 双环公司 | Trimmed lock-up clutch |
| TWI662620B (en)* | 2015-12-15 | 2019-06-11 | 台灣積體電路製造股份有限公司 | Semiconductor device structure and method for forming the same |
Also Published As
| Publication number | Publication date |
|---|---|
| US6853030B2 (en) | 2005-02-08 |
| US20030151099A1 (en) | 2003-08-14 |
| TW405252B (en) | 2000-09-11 |
| KR100335579B1 (en) | 2002-06-20 |
| US6541823B1 (en) | 2003-04-01 |
| KR19990006429A (en) | 1999-01-25 |
| JPH1167927A (en) | 1999-03-09 |
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