Patent ID: 8896069

Claim:
A semiconductor structure comprising: a relaxed, epitaxially grown straining material on a polysilicon layer of a gate stack structure, wherein: the gate stack structure is a PFET gate stack structure; the relaxed, epitaxially grown straining material is Si:C; and a lattice constant of the relaxed, epitaxially grown straining material is smaller than a lattice constant of the polysilicon layer of the gate stack structure; a substrate; a second relaxed, epitaxially grown straining material on a polysilicon layer of a second gate stack structure, wherein: the second gate stack structure is an NFET gate stack structure; the second gate stack structure includes sidewalls and spacers; the second relaxed, epitaxially grown straining material includes a planar surface that is above the second gate stack structure and that extends laterally above the sidewalls and the spacers; the second relaxed, epitaxially grown straining material is SiGe; and an intrinsic lattice constant of the second relaxed, epitaxially grown straining material is larger than a lattice constant of the polysilicon layer of the second gate stack structure; and a shallow trench isolation structure in the substrate between the PFET gate stack structure and the NFET gate stack structure, wherein: the SiGe material fills a first recess in a source region of the PFET gate stack structure; the SiGe material fills a second recess in a drain region of the PFET gate stack structure; and an oxide cap is formed directly on a top surface of the polysilicon layer of the PFET gate stack structure, the oxide cap having a topmost surface that is within a recess formed in the PFET gate stack structure.