Techniques for evaluating the surface potential and the effective surface mobility of a m.o.s. transistor are described. These techniques include determination of the fixed oxide charge density, the surface-state charge density and the average donor concentration. The surface potential is evaluated as a function of gate voltage, because this dependence is necessary in order to calculate the density of surface states from charge-pumping measurements. The effective surface mobility is evaluated as a function of bias, because this dependence is necessary in order to develop a bias-dependent 1/fnoise model of a m.o.s. transistor.