Abstract: Si/SiGe/SOI quantum-well p-MOSFETs were simulated in this paper and the impact of Sicap layer thickness on Ge inter-diffusion was investigated with emphasis. It has been verified that these models are capable for data analysis. It has been found that thin Si-cap layer contributed to abrupt Si/SiGe hetero-junction and high-qualify quantum-well which confines holes more effectively in the SiGe layer than thick Si-cap. Moreover,optimized Si-cap layer thickness offered the highest parallel electric field which is also an important factor to boost the drain current.