  Based on Monte Carlo simulation, we report the study of the inversion layer
mobility in n-channel strained Si/ Si1-xGex MOS structures. The influence of
the strain in the Si layer and of the doping level is studied. Universal
mobility curves mueff as a function of the effective vertical field Eeff are
obtained for various state of strain, as well as a fall-off of the mobility in
weak inversion regime, which reproduces correctly the experimental trends. We
also observe a mobility enhancement up to 120 % for strained Si/ Si0.70Ge0.30,
in accordance with best experimental data. The effect of the strained Si
channel thickness is also investigated: when decreasing the thickness, a
mobility degradation is observed under low effective field only. The role of
the different scattering mechanisms involved in the strained Si/ Si1-xGex MOS
structures is explained. In addition, comparison with experimental results is
discussed in terms of SiO2/ Si interface roughness, as well as surface
roughness of the SiGe substrate on which strained Si is grown.
