Method for producing semiconductor substrate, method for producing field effect transistor, semiconductor substrate, and field effect transistor

Abstract

In a semiconductor substrate, a field effect transistor, and methods for producing the same, in order to lower threading dislocation density and also to lower surface roughness, a step of repeating, a plurality of times, a process of epitaxially growing a SiGe gradient composition layer of which a Ge composition ratio is gradually increased from a Ge composition ratio of a base material and a process of epitaxially growing a SiGe constant-composition layer on the gradient composition layer at a final Ge composition ratio of the gradient composition layer, thereby depositing a SiGe layer of which a Ge composition ratio changes in a film deposition direction, in a step-like manner with a gradient, a heat treatment step of performing heat treatment at a temperature exceeding a temperature of the epitaxial growth either during or after formation of the SiGe layer, and a polishing step of polishing to remove irregularities on a surface of the SiGe layer which arise in the heat treatment after formation of the SiGe layer are included.