PURPOSE: A method for fabricating a semiconductor device is provided to improve product reliability by forming a thickness of a metal gate formed on an active which is the same as the thickness of a metal gate formed on a second element isolation layer. CONSTITUTION: A first element isolation layer and a second element isolation layer are formed in a semiconductor substrate(S100). A dry cleaning and a wet etching process are performed on the semiconductor substrate(S110). A transistor is formed on the semiconductor substrate(S120). [Reference numerals] (AA) Start; (BB) End; (S100) Form a first and a second element isolation layer on a semiconductor substrate; (S110) Dry-cleaning and wet-etching the semiconductor substrate; (S120) Form a transistor on the semiconductor substrate
