US Patent 10923595 Semiconductor device having a SiGe epitaxial layer containing Ga

A semiconductor device includes a field effect transistor (FET). The FET includes a channel region and a source/drain region disposed adjacent to the channel region. The FET also includes a gate electrode disposed over the channel region. The FET is an n-type FET and the channel region is made of Si. The source/drain region includes an epitaxial layer including Si1−x−yM1xM2y, where M1 is one or more of Ge and Sn, and M2 is one or more of P and As, and 0.01≤x≤0.1.