Multi-layer source/drain stressor

摘要

A method for forming a semiconductor device includes forming a recess in a source region and a recess in a drain region of the semiconductor device. The method further includes forming a first semiconductor material layer in the recess in the source region and a second semiconductor material layer in the recess in the drain region, wherein each of the first semiconductor material layer and the second semiconductor material layer are formed using a stressor material having a first ratio of an atomic concentration of a first element and an atomic concentration of a second element, wherein the first element is silicon and a first level of concentration of a doping material. The method further includes forming additional semiconductor material layers overlying the first semiconductor material layer and the second semiconductor material layer that have a different ratio of the atomic concentration of the first element and the second element.