A semiconductor device includes an epitaxial straining region formed within a semiconductor substrate, the straining region being positioned adjacent to a gate stack, the gate stack being positioned above a channel. The straining region comprises a defect comprising two crossing dislocations such that a cross-point of the dislocations is closer to a bottom of the straining region than to a top of the straining region. The straining region comprises an element with a smaller lattice constant than a material forming the substrate.