Abstract: A method for forming a metal silicide layer, a semiconductor device and a method for fabricating the device are disclosed. Through depositing a buffer layer between a metal layer and a substrate, metal atoms in the metal layer will diffuse, during a thermal annealing process, through the buffer layer into the substrate while being buffered by the buffer layer. As a result, the diffusion speed and depth of the metal atoms in the substrate are both reduced, and a reaction between the metal and silicon in the substrate is hence slowed down. In this way, the risk of agglomeration of the resulting metal silicide can be effectively lowered, avoiding pinhole defects occurring in the substrate and improving the interface roughness of the resulting metal silicide layer.