A method for forming a semiconductor device comprises a step of providing a substrate whose surface has gate structures, wherein two sides of each gate structure has an interconnection region respectively, portions, in the interconnection regions, of the substrate have source regions and drain regions positioned at two sides of the corresponding gate structure respectively, and surfaces of the substrate and the gate structures have a first dielectric layer; a step of forming a barrier layer on the surface of the first dielectric layer, wherein the material of the barrier layer is different from that of the first dielectric layer, and the pattern of the barrier layer at least penetrates one interconnection region; a step of forming a first patterned layer with a first opening on the first dielectric layer and the surface of the barrier layer, wherein the first opening exposes the positions of the interconnection regions; a step of taking the first patterned layer and the barrier layer as mask layers, and etching the first dielectric layer until the surface of the substrate in the interconnection regions is exposed, so as to form source-drain grooves; a step of forming gate through holes in the first dielectric layer for exposing tops of the gate structures; and a step of forming source-drain conductive structures in the source-drain grooves and forming gate plugs in the gate through holes. The formed semiconductor device is good in appearance and has improved performances.