Semiconductor structure and forming method thereof

The invention discloses a semiconductor structure and a forming method thereof, and the method comprises the steps: providing a substrate, forming a gate structure on the substrate, forming a source-drain doping layer in the substrate at two sides of the gate structure, and forming an initial dielectric layer covering the substrate and the gate structure on the substrate, the initial dielectric layer comprises a first dielectric layer covering the side wall of the gate structure and a sacrificial dielectric layer higher than the top of the gate structure; forming an opening for exposing the top of the source-drain doping layer in the initial dielectric layer between the adjacent gate structures; forming a sacrificial side wall covering the side wall of the opening; forming a conductive plug in the opening after the sacrificial side wall is formed; removing the sacrificial dielectric layer to expose part of the sacrificial side wall of the side wall of the conductive plug; removing partial width of the sacrifi