A semiconductor device includes: a substrate; a fin structure and a gate structure formed on the substrate; and a source/drain trench formed in the fin structure on each side of the gate structure. The source/drain trench includes a bottom region and a top region located above the bottom region. Along an extension direction of the fin structure, a dimension of the top region is larger than a dimension of the bottom region. Along the extension direction of the fin structure, a shortest distance from a sidewall surface of the top region of the source/drain trench to a sidewall surface of the gate structure is smaller than a shortest distance from a sidewall surface of the bottom region of the source/drain trench to the sidewall surface of the gate structure. The semiconductor device further includes a source/drain doped layer formed in the source/drain trench.