A method for manufacturing a semiconductor device including: preparing a semiconductor substrate with a gate oxide layer on the top thereof; depositing a polycrystalline silicon layer on the top of the semiconductor substrate; depositing a protection layer overlying the top of the polycrystalline silicon layer; etching the protection layer and the polycrystalline silicon layer to form a gate body block; forming an oxide layer overlying the gate body block and the semiconductor substrate; polishing the oxide layer through Chemical Mechanical Polishing (CMP) until the top of the gate body block; removing the protection layer on the top of the gate body block; and forming a metal silicide layer on the gate body block.