A comparison of wave-function penetration effects on gate capacitance in deep submicron n- and p-MOSFETs

We have calculated the effects of wave function penetration into the gate-oxide on the modeling of gate capacitance in deep submicron p-MOSFETs on [100] silicon for the first time. These results are compared to those of n-MOSFETs. Self-consistent calculations show that contrary to the common belief, penetration effects are more pronounced in p-MOS devices. The error in inversion capacitance due to neglect of penetration effects has opposite dependence on substrate doping density for n-MOS and p-MOS structures. Consequently, the error in gate capacitance for an n-MOSFET in strong inversion is strongly dependent on doping density, while that for a p-MOSFET essentially does not depend on doping density. An explanation for this unusual result is also provided. Although the error in gate capacitance is only a few percent, it will have nontrivial effects on device parameter extraction from capacitance-voltage (C-V) measurements.