Isolation trench processing for strain control

Abstract

A semiconductor fabrication process includes forming a hard mask, e.g., silicon nitride, over an active layer of a silicon on insulator (SOI) wafer, removing a portion of the hard mask and the active layer to form a trench, and forming an isolation dielectric in the trench where the dielectric exerts compressive strain on a channel region of the active layer. Forming the dielectric may include performing a thermal oxidation. Before performing the thermal oxidation, semiconductor structures may be formed, e.g., by epitaxy, on sidewalls of the trench. The structures may be silicon or a silicon compound, e.g., silicon germanium. During the thermal oxidation, the semiconductor structures are consumed. In the case of a silicon germanium, the germanium may diffuse during the thermal oxidation to produce a silicon germanium channel region.