An analytical model for MOSFET local oxide capacitance

Practically all methods for extraction of the lateral interface state density profile N_it(x) from charge-pumping data employ the oxide capacitance C_ox [1-3] as a crucial parameter. Although Lee et al. [2] claimed that the coordinate dependence of the capacitance C_ox(x) due to the fringing effect should be respected, usually C_ox is treated as a constant parameter of the device [3]: C_ox=ε_ox/t_ox, (1), where t_ox is the oxide thickness at the center of the device and ε_ox is the dielectric permittivity. However, the electric field non-uniformity is of special importance for the extraction of the interface state density profile after hot-carrier stress because the N_it(x) peak is located near the drain end of the gate [4] where the capacitor non-ideality is most pronounced.