Characterization of inversion-layer capacitance of holes in Si MOSFET's

Inversion-layer capacitance (C-inv) in p-channel Si MOSFET's is studied exp erimentally and theoretically with emphasis on the surface carrier concentr ation (N-s) dependence, which is important in the quantitative description and the physical understanding. The amount of C-inv and its influence on th e gate capacitance are compared between electron and hole inversion layers. It is experimentally verified that, under same physical thickness of gate oxides, the electrical gate oxide thickness, determined from the gate capac itance, is larger for inversion-layer holes than that for inversion-layer e lectrons, because of smaller values of C-inv for inversion-layer holes. Self-consistent Poisson-Schrodinger calculation of C-inv is performed on ba sis of the approximation of a constant effective mass and is compared with the experimental C-inv. It is found that the calculation using the effectiv e masses at the valence band edge can accurately represent the experimental results over a whole range of N-s.