Patent ID: 7405142

Claim:
A method of manufacturing a semiconductor substrate in which an SiGe layer is grown epitaxially on Si substrate, comprising: a first layer formation process of epitaxially growing a first SiGe layer on said Si substrate; a second layer formation process of epitaxially growing a second SiGe layer either directly onto said first SiGe layer, or with an epitaxially grown Si layer intervening; a heat treatment process of performing heat treatment, either during or after formation by epitaxial growth of said SiGe layers, at a temperature exceeding the epitaxial growth temperature; and a polishing process of removing by polishing the irregularities in the surface caused by said heat treatment, wherein in said first layer formation process, the film thickness of said first SiGe layer is set to be thinner than twice the critical film thickness, which is the film thickness at which dislocations arise and lattice relaxation occurs due to increasing film thickness; in said second layer formation process, the Ge composition ratio in the second SiGe layer is, at least at the contact face with the first SiGe layer or with the Si layer, set lower than the maximum value of the Ge composition ratio in the first SiGe layer, and moreover a gradient composition region is formed in at least a portion of which the Ge composition ratio rises gradually in moving toward the surface; and said polishing process is performed after formation of said second SiGe layer.