MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) provided with GeSn source and drain and forming method thereof

The invention provides an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) provided with a GeSn source and drain and a forming method thereof. The forming method comprises the following steps: providing a substrate of which the top is provided with a Ge layer; forming a gate stack or a fake gate on the substrate; forming openings of a source area and a drain area in both sides of the gate stack or the fake gate, and exposing the Ge layer out of the openings; injecting atoms, molecules, ions or plasmas containing Sn elements into the surface layer of the Ge layer, and forming a GeSn layer in the openings. By adopting the forming method of the MOSFET, a field effect transistor provided with the GeSn source and drain can be formed. Since the thicknesses of the GeSn source and drain are small, and the crystal quality is good, the transistor has high electric performance. Moreover, the method has the advantages of easiness, practicability and low cost.