A semiconductor structure and a method for forming the semiconductor structure are provided. The semiconductor structure includes a substrate and a dummy gate structure on the substrate. The substrate contains source-drain openings on both sides of the dummy gate structure. The semiconductor structure also includes a first stress layer formed on a sidewall of a source-drain opening of the source-drain openings. Further, the semiconductor structure includes a second stress layer formed at a bottom of the source-drain opening and on the first stress layer. The second stress layer fully fills the source-drain opening, and stress of the first stress layer is less than stress of the second stress layer.