A vertical metal oxide semiconductor (VMOS) is a type of metal oxide semiconductor (MOS) transistor, so named because of the V-shaped groove which is vertically cut into the substrate to act as the gate of the transistor to allow the delivery of a higher amount of current coming from the source towards the “drain” of the device.
A vertical metal oxide semiconductor is also known as a V-groove MOS.
A vertical metal oxide semiconductor is constructed by forming four different diffused layers in silicon and then etching a V-shaped groove in the middle vertically at a precisely controlled depth through the layers. The gate electrode is then formed within the V-shaped groove by depositing metal, usually gallium nitride (GaN), over silicon dioxide in the groove.
VMOS has been primarily used as a “stop-gap” power device until better geometries such as the UMOS or trench-gate MOS were introduced, which creates a lower electric field at the top which then leads to higher maximum voltages than what is possible with VMOS transistors.