Patent ID: 7888747

Claim:
A semiconductor device, comprising: a semiconductor substrate comprising first and second transistor regions that are isolated by an element isolation region; a first impurity diffusion suppression layer formed on the semiconductor substrate in the first transistor region; a second impurity diffusion suppression layer formed on the semiconductor substrate in the second transistor region, and having a thickness larger than that of the first impurity diffusion suppression layer; a first crystal layer formed on the first impurity diffusion suppression layer; a second crystal layer formed on the second impurity diffusion suppression layer; a first gate electrode formed on the first crystal layer via a first gate insulating film; a second gate electrode formed on the second crystal layer via a second gate insulating film; a first channel region formed in a region in the semiconductor substrate, the first impurity diffusion suppression layer and the first crystal layer below the first gate electrode in the first transistor region, and containing a first p-type impurity; a second channel region formed in a region in the semiconductor substrate, the second impurity diffusion suppression layer and the second crystal layer below the second gate electrode in the second transistor region, and containing a second p-type impurity; first source/drain regions formed on both sides of the first channel region; and second source/drain regions formed on both sides of the second channel region; wherein a concentration of the first p-type impurity in a region of the first channel region in the first crystal layer is lower than that in a region of the first channel region in the semiconductor substrate; and a concentration of the second p-type impurity in a region of the second channel region in the second crystal layer is lower than that in a region of the second channel region in the semiconductor substrate.