Patent ID: 7479422

Claim:
A method for forming a semiconductor device, comprising: providing a substrate region having a first material and a second material overlying the first material, wherein the first material has a different lattice constant from a lattice constant of the second material; forming a gate in the substrate region having the second material; etching a first opening on a first side of the gate and etching a second opening on a second side of the gate, wherein each of the first opening and the second opening extends into the substrate region having the first material; creating a first in-situ doped epitaxial region in the first opening and the second opening, wherein the first in-situ doped epitaxial region is created using silicon and has a first doping type; and creating a second in-situ doped expitaxial region overlying the first in-situ doped epitaxial region in the first opening and the second opening, wherein the second in-situ doped epitaxial region is created using silicon and has a second doping type different from the first doping type; wherein the first material is relaxed silicon germanium and the second material is relaxed silicon.