A semiconductor layer 30 of a graded SiGe-HDTMOS is constructed of an upper Si film 12, an Si buffer layer 13, an Si1−xGex film 14 and an Si cap layer 15. The region between a source region 20a and drain region 20b of the semiconductor layer 30 includes a high concentration n-type Si body region 22 and an n Si region 23, an Si cap region 25 and an SiGe channel region 24. A Ge composition ratio x of the Si1−xGex film 14 is made to increase from the Si buffer layer 13 to the Si cap layer 15. For the p-type HDTMOS, the electron current component of the substrate current decreases.