US Patent 7241647 Graded semiconductor layer

A process for forming a semiconductor device. The process includes forming a template layer for forming a layer of strained silicon. In one example a layer of graded silicon germanium is formed where the germanium is at a higher concentration at the lower portion and at a lower concentration at a top portion. When subject to a condensation process, the germanium of the top portion of the layer diffuses to a remaining portion of the silicon germanium layer. Because the silicon germanium layer has a higher concentration of germanium at lower portions, germanium pile up after condensation may be reduced at the upper portion of the remaining portion of the silicon germanium layer.