The comprehensive Ando’s surface roughness (SR) model examined for nMOSFETs. Four distinct source terms contribute in SR scattering. Relative strength of these contributing source terms are evaluated and compared. The most influential term turned out to be due to scattering with the “physical steps” at the interface. Remote SR scattering is also significant in ultra-thin MOS structures. The proposed model of Gámiz et al. for remote SR scattering is studied. It is shown that modification to the Gámiz model is necessary in order to observe the full impact of rms height of the abrupt “steps”.