Strained silicon with elastic edge relaxation

A semiconductor device comprising at least one n-channel MOSFET, the semiconductor device comprising:

• a substrate comprising silicon and having first and second walls of one or more shallow trench isolation structures extending partially into the substrate, a substrate interface region extending from the first wall to the second wall;
• a first layer comprising germanium on the substrate interface region, the first layer extending for a first spacing between the first and second walls, the first layer having a thickness less than a first thickness at which misfit dislocations form in the first layer due to a lattice mismatch between the first layer and the substrate;
• a second layer comprising silicon formed on the first layer, the second layer extending between the first and second walls;
• and
• a gate dielectric layer on the second layer separating the second layer from a gate electrode so that the second layer provides at least a part of a channel of an n-channel MOSFET device,
• wherein a concentration of germanium in the first layer is greater than a concentration of germanium in the second layer, and wherein the first spacing is such that the first layer induces a strain in the substrate interface region and in the second layer over an extent of the first spacing.