In order to describe the electron mobility enhancement in inversion layer in strained-Si on Si1-xGex n type metal-oxide-semiconductor field-effect transistors (nMOSFETs), a new physically-based electron mobility model is presented in the paper. This model can not only show the dependence of acoustic phonon-limited mobility and surface roughness-limited mobility on transverse electrical field normal to the semiconductor-insulator interface, but also explains the electron mobility enhancement mechanism due to scattering suppression caused by germanium (Ge) content. The expression of the new model is simple and can simulate the mobility for any Ge content. Numerical analysis results show that this model fits the reported experimental data very well. In addition, this model can be easily included in the device simulator ISE and gives good agreement with simulated results of device simulator with built-in model.