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A new precise C-V model of a semiconduction - insulator - semiconductor (SIS) by using Fermi - Dirac statistics is investigated to replace the Boltzman approximation. The degenerate and bandgap narrowing effect are also taken into consideration. Using the precise model, we get the relationship between electron doping concentration and the Fermi - level. It can also be used to get the precise prediction of surface energy bending, two respective surface charges in the respective capacitors and two respective widths due to surface charge depletion or accumulation. On the other hand, based on the precise C-V model we investigate a new precise simulation prediction of the temperature - coefficient of capacitor (Tcc). It is found that the temperature dependence of dielectric - constant is the major component in Tcc. By lowing the polysilicon doping concentration and thinning oxide thickness, Tcc can be reduced significantly. No matter simulated voltage or temperature - coefficient of capacitor, the most importance of these three parameters for simulation rediction are the oxide thickness, the top and bottom plate carrier doping concentrations of capacitor. To get a low voltage/temperature - coefficient of capacitor, it needs to find the optimize condition of these three parameters.
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