Patent ID: 8735303

Claim:
A method of forming first PFET transistor in and above a first active region of a semiconducting substrate and a second PFET transistor in and above a second active region of said semiconducting substrate, the method comprising: forming a first recess in said first active region of said semiconducting substrate while masking said second active region; forming a first layer of channel semiconductor material for said first PFET transistor in said first recess; performing a first thermal oxidation process to form a first protective layer on said first layer of channel semiconductor material; forming a second recess in said second active region of said semiconducting substrate; forming a second layer of channel semiconductor material for said second PFET transistor in said second recess; and performing a second thermal oxidation process to form a second protective layer on said second layer of channel semiconductor material, wherein at least one of a thickness of said first and second layers of channel semiconductor materials or a concentration of germanium in said first and second layers of channel semiconductor materials are different.