US Patent 7696537 Step-embedded SiGe structure for PFET mobility enhancement

A device, and method for manufacturing the same, including a PFET having an embedded SiGe layer where a shallow portion of the SiGe layer is closer to the PFET channel and a deep portion of the SiGe layer is further from the PFET channel. Thus, the SiGe layer has a boundary on the side facing toward the channel that is tapered. Such a configuration may allow the PFET channel to be compressively stressed by a large amount without necessarily substantially degrading extension junction characteristics. The tapered SiGe boundary may be configured as a plurality of discrete steps. For example, two, three, or more discrete steps may be formed.