METHOD FOR PRODUCING SEMICONDUCTOR SUBSTRATE AND METHOD FOR FABRICATING FIELD EFFECT TRANSISTOR AND SEMICONDUCTOR SUBSTRATE AND FIELD EFFECT TRANSISTOR

摘要

A semiconductor substrate, a field effect transistor, and its fabricating method comprising a step for forming an SiGe layer where the compositional ratio of Ge varies stepwise with an inclination in the film depositing direction on an Si substrate in order to decrease through dislocation density and surface roughness by repeating a plurality of times a step for epitaxially growing an inclining composition layer of SiGe where the Ge compositional ratio increases gradually from that of an underlying material and a step for epitaxially growing a constant composition layer of SiGe on the inclining composition layer with the final compositional ratio of Ge of the inclining composition layer, a step for heat treating the SiGe layer during or after formation thereof at a temperature exceeding the epitaxially growth temperature, and a step for removing, by polishing, irregularities generated on the surface by heat treatment after forming the SiGe layer.