Patent ID: 8076223

Claim:
A method for producing a semiconductor substrate, comprising at least steps of: forming a SiGe gradient composition layer having a Ge concentration increasing with thickness toward a surface thereof on a Si single crystal substrate; forming a SiGe constant composition layer having a constant Ge concentration on the SiGe gradient composition layer; flattening a surface of the SiGe constant composition layer; removing a natural oxide film on the flattened surface of the SiGe constant composition layer; and forming a strained Si layer on the surface of the SiGe constant composition layer from which the natural oxide film has been removed, wherein the formation of the SiGe gradient composition layer and the formation of the SiGe constant composition layer are performed at a temperature T 1 that is higher than 800° C., the removal of the natural oxide film from the surface of the SiGe constant composition layer is performed in a reducing atmosphere through a heat treatment at a temperature T 2 that is equal to or higher than 800° C. and lower than the temperature T 1 , the formation of the strained Si layer is performed using monosilane at a temperature T 3 of 500° C. to 700° C., and after the step of removing the natural oxide film from the surface of the SiGe constant composition layer and before the growth of the strained Si layer, a Si cap layer is formed on the surface of the SiGe constant composition layer, from which the natural oxide film has been removed, at a temperature lower than the temperature T 1 .