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

Abstract

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, which enable the threading dislocation density of the SiGe layer to be reduced and the surface roughness to be minimized. On top of a Si substrate is provided a SiGe buffer layer constructed of a plurality of laminated layers comprising 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.