Disclosed are embodiments of a metal oxide semiconductor field effect transistor (MOSFET) structure and a method of forming the structure. The structure incorporates source/drain regions and a channel region between the source/drain regions. The source/drain regions can comprise silicon, which has high diffusivity to the source/drain dopant. The channel region can comprise a silicon alloy selected for optimal charge carrier mobility and band energy and for its low source/drain dopant diffusivity. During processing, the source/drain dopant can diffuse into the edge portions of the channel region. However, due to the low diffusivity of the silicon alloy to the source/drain dopant, the dopant does not diffuse deep into channel region. Thus, the edge portions of the silicon alloy channel region can have essentially the same dopant profile as the source/drain regions, but a different dopant profile than the center portion of the silicon alloy channel region.