Patent ID: 7875521

Claim:
A method of manufacturing a semiconductor device comprising: forming a gate insulating film over a silicon substrate; forming a gate electrode over the gate insulating film; implanting a first impurity having a conductivity type into the silicon substrate using the gate electrode as a mask; forming a first side wall insulating film on a side wall of the gate insulating film and the gate electrode, a portion of the first side wall insulating film extending on the silicon substrate; forming a second side wall insulating film on the first side wall insulating film; implanting a second impurity having said conductivity type into the silicon substrate using the gate electrode, the first side wall insulating film and the second side wall insulating film as masks; forming a trench in the silicon substrate by etching the silicon substrate using the gate electrode, the first side wall insulating film and the second side wall insulating film as masks; removing a portion of the first side wall insulating film to form a concave portion between the silicon substrate and the second side wall insulating film; and; forming a semiconductor mixed crystal layer in the trench and in the concave portion.