SEMICONDUCTOR SUBSTRATE, FIELD EFFECT TRANSISTOR, METHOD OF FORMING SiGe LAYER AND METHOD OF FORMING STRAINED Si LAYER USING SAME, AND METHOD OF MANUFACTURING FIELD EFFECT TRANSISTOR

摘要

PURPOSE: A semiconductor substrate, a field effect transistor, a method of forming a SiGe layer and a method of forming a strained Si layer using the same, and a method of manufacturing a field effect transistor are provided to reduce the threading dislocation density of the SiGe layer and to minimize the surface roughness. CONSTITUTION: On top of a Si substrate(1) is provided a SiGe buffer layer(2) constructed of a plurality of laminated layers having alternating layers of a SiGe gradient composition layer in which the Ge composition ratio increases gradually from the Ge composition ratio of the base material, and a SiGe constant composition layer which is provided on top of the gradient composition layer and in which the Ge composition ratio is equal to that of the upper surface of the gradient composition layer.