In compact transistor modeling for circuit simulation, the capacitances of conventional MOS devices are commonly determined as the derivatives of terminal charges, which on their turn are obtained from the so-called Ward-Dutton charge partitioning scheme (Ward, 1981). For devices with a laterally non-uniform channel doping profile, however, it is shown in this paper that: 1) no terminal charges exist for the description of capacitances. Instead, 2) a model is presented for the capacitances of such devices, including numerical results for a MOS transistor with a laterally diffused channel doping profile. Finally, 3) a method is given to incorporate such a capacitance model in circuit simulators which are traditionally based on terminal charge models.
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