Capacitance modeling of laterally non-uniform MOS devices

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.