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AVMOS (/ˈviːmɒs/) (vertical metal oxide semiconductor orV-groove MOS) transistor is a type of metal–oxide–semiconductor field-effect transistor (MOSFET). VMOS is also used to describe the V-groove shape vertically cut into the substrate material.[1]
The "V" shape of theMOSFET'sgate allows the device to deliver a higher amount ofcurrent from thesource to the drain of the device. The shape of thedepletion region creates a wider channel, allowing more current to flow through it.
During operation in blocking mode, the highest electric field occurs at the N+/p+ junction. The presence of a sharp corner at the bottom of the groove enhances the electric field at the edge of the channel in the depletion region, thus reducing the breakdown voltage of the device.[2] This electric field launches electrons into the gate oxide and consequently, the trapped electrons shift the threshold voltage of the MOSFET. For this reason, the V-groove architecture is no longer used in commercial devices.
The device's use was apower device until more suitable geometries, like theUMOS (or Trench-Gate MOS) were introduced in order to lower the maximumelectric field at the top of the V shape and thus leading to higher maximum voltages than in case of the VMOS.
TheMOSFET was invented at Bell Labs between 1955 and 1960.[3][4][5][6][7][8] The V-groove construction was pioneered byJun-ichi Nishizawa in 1969,[9] initially for thestatic induction transistor (SIT), a type of junctionfield-effect transistor (JFET).[10]
The VMOS was invented byHitachi in 1969,[11] when they introduced the first verticalpower MOSFET in Japan.[12]T. J. Rodgers, while he was a student atStanford University, filed aUS patent for a VMOS in 1973.[13]Siliconix commercially introduced a VMOS in 1975.[11] The VMOS later developed into what became known as the vertical DMOS (VDMOS).[14]
In 1978,American Microsystems (AMI) released the S2811.[15][16] It was the firstintegrated circuit chip specifically designed as adigital signal processor (DSP), and was fabricated using VMOS, a technology that had previously not been mass-produced.[16]
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