US Patent 8956951 Method for manufacturing SOI wafer

A method for manufacturing an SOI wafer includes performing a flattening heat treatment on an SOI wafer under an atmosphere containing an argon gas, in which conditions of SOI wafer preparation are set so that a thickness of an SOI layer of the SOI wafer to be subjected to the flattening heat treatment is 1.4 or more times thicker than that of a BOX layer, and the thickness of the SOI layer is reduced to less than a thickness 1.4 times the thickness of the BOX layer by performing a sacrificial oxidation treatment on the SOI layer of the SOI wafer after the flattening heat treatment.