Enhancement MOSFET A p-channel enhancement MOSFET consists of lightly doped n-substrate. Into which two heavily doped p + regions are diffused. These two p + source and the drain. A thin layer of siO 2 is grown over the surface of the entire assembly. Holes are cut into this Si O 2 layer for making contact with p + source and drain regions. On the SiO 2 layer, a metal (aluminium) layer is overlaid coveting the entire channel region from source to drain. This aluminium layer constitutes the gate. The area of MOSFET is typically 5 square miles or less. This area is extremely small being only about 5% of the area required for a bipolar junction transistor. A parallel plate capacitor is formed with the metal area of the gate and the semiconductor channel acting as the electrodes of the capacitor. The oxide layer acts as the dielectric between the electrodes. Working of Enhancement MOSFET ...