To obtain a semiconductor substrate having a high-quality Ge-based epitaxial film in a large area, a SiGe mixed crystal buffer layer and a Ge epitaxial film is grown on a main surface of a Si substrate 10. Although high-density defects are introduced in the Ge epitaxial film 11 from an interface between the Ge epitaxial film 11 and the Si substrate 10, the Ge epitaxial film is subjected to a heat treatment at a temperature of not less than 700° C. and not more than 900° C. to cause threading dislocations 12 to change into dislocation-loop defects 12′ near the interface between the Ge epitaxial film 11 and the Si substrate. A main surface of at least one of the Ge epitaxial film 11 with an ion implanted layer and a support substrate 20 is then subjected to a plasma treatment or ozone treatment for the purpose of surface cleaning, surface activation, and the like, after which the main surfaces of the Ge epitaxial film 11 and the support substrate 20 are appressed against and bonded to each other with their surfaces being determined as the joint surfaces. An external impact is then applied to the bonding interface, causing the Ge epitaxial film to be delaminated along a hydrogen ion implanted interface 13, thus obtaining a Ge thin film 14. A surface of the Ge thin film 14 is subsequently subjected to a final surface treatment (for example, CMP) to remove the damage caused by the hydrogen ion implantation, thus resulting in a GeOI substrate having the Ge thin film 14 on the surface thereof.