A unified modeling approach for the submicrometer MOS transistor charge/cap
acitance characteristics in all operation regions is presented. Development
of this MOS charge model is based on the charge-density approximation to r
educe the complexity of the analytical expression. To model the charge dens
ity more accurately, the conductance-degradation coefficient is determined
by the derivative of drain-to-source saturation voltage with respect to gat
e-to-channel potential. The unified charge densities in gate, channel, and
bulk regions are obtained with the assistance of the sigmoid, hyperbola, an
d exponential interpolation techniques. Good agreement between the measurem
ent data and simulation results is obtained.