A semiconductor device comprises a substrate; a shallow trench isolation embedded in the substrate and forms at least one opening region; a channel region located in the opening region; a gate stack including a gate dielectric layer and a gate electrode layer, located above said channel region; a source/drain region located on both sides of the channel region, including a stress layer which provides strain for the channel region. A liner layer is provided between the shallow trench isolation and the stress layer, which serves as a crystal seed layer of the stress layer. A liner layer and a pad oxide layer are provided between the substrate and the shallow trench isolation. The liner layer is inserted between the STI and the stress layer of the source/drain region as a crystal seed layer or nucleating layer for epitaxial growth, thereby eliminating the STI edge effect during the source/drain strain engineering.