Patent ID: 8288760

Claim:
A field effect transistor comprising: a semiconductor substrate containing Si atoms; a protruding structure formed on the semiconductor substrate; a channel region formed in the protruding structure and containing Ge atoms; an insulating film embedded under the channel region; source/drain regions formed at sides of the channel region and containing Si and Ge atoms, a Ge composition ratio among Si and Ge atoms contained in the source/drain regions being lower than a Ge composition ratio among Si and Ge atoms contained in the channel region; channel side regions formed between the channel region and the source/drain regions at sides of the channel region and containing Si and Ge atoms, a Ge composition ratio among Si and Ge atoms contained in the channel side regions continuously changing from the channel region sides to the source/drain region sides; a gate insulating film formed on the channel region; and a gate electrode formed on the gate insulating film on the channel region.