From the physical insights provided by the universal effective mobility versus effective vertical electric field curve for electrons in MOS inversion layers, a simple general expression for the gate voltage dependence of the effective electron mobility is derived for use in SPICE circuit simulation. This expression is quite accurate over a wide range of channel doping concentrations and gate oxide thicknesses, without the need for fitting parameters, such as the theta parameter of the current SPICE level 3 mobility degradation model. It is, therefore, a much more universal model than the present SPICE level 3 mobility expression. Furthermore, the relative accuracy of this new model compared to the current SPICE model is expected to increase at the higher vertical electric fields typical of submicrometer oxide semiconductor field effect transistors (MOSFETs).>