A MOS FET with a bulk channel (Theory)

Analytical expressions are obtained for calculating the volt-ampere characteristic of MOS FETs in such a way as to allow for, in explicit form, the density of the surface states at the dielectric-semiconductor interface and the charge embedded in the dielectric. The characteristic is calculated in the approximation of a 'smooth' channel (Shockley, 1952); this makes it possible to use Poisson's equation in one dimension for each point in the channel of the MOS FET along the y axis. The expressions obtained are valid for MOS FETs operating both in the depletion and the enhancement mode of the channel.