The objective is to improve capabilities such as high-speed switching of a compound semiconductor device. Provided is a semiconductor wafer comprising a silicon wafer; an insulating film that is formed on the silicon wafer and that has an open portion reaching the silicon wafer; a Ge crystal formed in the open portion; a seed compound semiconductor crystal that is grown with the Ge crystal as a nucleus and that protrudes beyond a surface of the insulating film; and a laterally grown compound semiconductor layer that is laterally grown on the insulating film with a specified surface of the seed compound semiconductor crystal as a seed surface.