QUANTITATIVE UNDERSTANDING OF INVERSION-LAYER CAPACITANCE IN SI MOSFETS

The inversion-layer capacitance (C-inv) in n-channel Si MOSFET's, is studied experimentally and theoretically with emphasis on the surface carrier concentration (N-s) dependence of C-inv, which is important in the quantitative description of the inversion-layer capacitance, Based on the experimental N-s and temperature dependencies, the physical origin of C-inv is discussed, It is shown that, at lower N-s, C-inv is determined by the finite effective density of states, while, at higher N-s, C-inv is determined quantum mechanically by the finite inversion-layer thickness, Also, the results of the surface orientation dependence of C-inv are presented as the first direct evidence for the fact that surface quantization plays a significant role in C-inv even at room temperature, The self-consistent Poisson-Schrodinger calculation of C-inv is performed and found to represent the experimental results accurately, The influence of C-inv on the gate capacitance is discussed in terms of the device scaling on basis of the experimental and calculated values of C-inv.