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 siO2 is grown over the surface of the
entire assembly. Holes are cut into this Si O2 layer for making
contact with p+ source and drain regions. On the SiO2
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
Drain Charecteristics of Enhancement MOSFET