This paper presents a detailed analysis of the multifrequency capacitance–voltage and conductance–voltage data of MOS capacitors. It is shown that the widely varied frequency dependence of the data from depletion to inversion can be fitted to various regional equivalent circuits derived from the full interface-state model. In certain regions, incorporating bulk-oxide traps in the interface-state model enables better fitting of data. By calibrating the model with experimental data, the interface-state density and the trap time constants are extracted as functions of energy in the bandgap, from which the stretch-out of gate voltage is determined. It is concluded that the commonly observed decrease of the 1-kHz capacitance toward stronger inversion is due to the increasing time constant for traps to capture majority carriers at the inverted surface.