a method for forming a polysilicon film in a plasma - assisted chemical vapor deposition system including a chamber in which a first electrode and a second electrode spaced apart from the first electrode are provided comprises providing a substrate on the second electrode , the substrate including a surface exposed to the first electrode , applying a first power to the first electrode for generating a plasma in the chamber , applying a second power to the second electrode during a nucleation stage of the polysilicon film for ion bombarding the surface of the substrate , and flowing an erosive gas into the chamber .