Patent ID: 7781771

Claim:
A semiconductor device comprising: a strained semiconductor body forming a heterojunction with a substrate semiconductor material, wherein said substrate semiconductor material is a first single crystal comprising a first group IV element, said first single crystal having a first lattice constant, and wherein said strained semiconductor body is a second single crystal comprising a second group IV element, said strained semiconductor body having a top surface and laterally opposite sidewalls; a semiconductor capping layer on the top surface and on the sidewalls of said strained semiconductor body, wherein said semiconductor capping layer is a third single crystal comprising said first group IV element; a gate dielectric layer on said semiconductor capping layer on said top surface and on said sidewalls of said strained semiconductor body; a gate electrode having a pair of laterally opposite sidewalls on said gate dielectric layer; and a pair of source/drain regions in said strained semiconductor body on opposite sides of said gate electrode, wherein the second single crystal at the heterojunction disposed below the gate dielectric layer is tetragonally distorted to have a second and third lattice constant, the second lattice constant along a plane parallel to the heterojunction and matched with the first lattice constant, the third lattice constant along a plane orthogonal to the heterojunction and mismatched with the first lattice constant.