Short-channel threshold model for buried-channel MOSFET's

An analytical closed-form expression for the short-channel threshold voltage of a normally-OFF-type buried-channel MOSFET (BC-MOSFET) was derived. The model is based on the increase in majority-carrier concentration along the channel and the substrate charge sharing property between source-drain and the channel. This model is able to predict the condition under which the magnitude of the threshold voltage can initially increase and then falls off precipitously as the channel length gradually decreases. Good agreement between theory and experiment was obtained with the p-channel BC-MOSFET used in the CMOS circuit.