This invention relates to a semiconductor device and a manufacturing method therefor for reducing stacking faults caused by high content of Ge in an embedded SiGe structure. The semiconductor device comprises a Si substrate with a recess formed therein. A SiGe seed layer is formed on sidewalls of the recess, and a first SiGe layer having a Ge content gradually increased from bottom to top is formed on the recess bottom. A second SiGe layer having a constant content of Ge is formed on the first SiGe layer. The thickness of the first SiGe layer is less than the depth of the recess. The Ge content in the SiGe seed layer is less than the Ge content in the second SiGe layer, and the Ge content at the upper surface of the first SiGe layer is less than or equal to the Ge content in the second SiGe layer.