Bulk non-planar transistor having strained enhanced mobility and methods of fabrication

1. 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.

2. The semiconductor device of claim 1 , wherein said semiconductor capping layer has a tensile strain.

3. The semiconductor device of claim 2 , wherein said semiconductor capping layer has greater tensile stress on the sidewalls of said strained semiconductor body than on the top surface of said strained semiconductor body.

4. The semiconductor device of claim 2 , wherein said source/drain regions are n type conductivity.

5. The semiconductor device of claim 1 , wherein said semiconductor substrate comprises a silicon substrate, wherein said strained semiconductor body comprises a silicon germanium alloy and wherein said semiconductor capping layer comprises a silicon film.

6. The semiconductor device of claim 1 , wherein said semiconductor capping layer has a compressive strain.

7. The semiconductor device of claim 6 , wherein said strained semiconductor body has tetragonal distortion and said semiconductor capping layer has a greater compressive strain on the sidewalls than on the top surface of said strained semiconductor body.

8. The semiconductor device of claim 6 , wherein said semiconductor substrate comprises a monocrystalline silicon substrate, wherein said strained semiconductor body comprises a silicon-carbon alloy and wherein said semiconductor capping layer comprises a single crystalline epitaxial silicon film.

9. The semiconductor device of claim 1 , wherein said semiconductor substrate comprises a silicon substrate, wherein said strained semiconductor body comprises a silicon germanium epitaxial body, and wherein said semiconductor capping layer comprises a single crystalline epitaxial silicon capping layer.

10. The semiconductor device of claim 1 , wherein a width of the semiconductor body is greater than a height of the semiconductor body.

11. The semiconductor device of claim 1 , wherein the semiconductor device comprises a tri-gate transistor.

12. The semiconductor device of claim 1 , wherein the semiconductor body comprises carbon.

13. The semiconductor device of claim 1 , wherein the semiconductor capping layer is orthorhombicly strained by the third lattice constant.