A method for manufacturing an aluminum oxide film for use in a semiconductor device, the method including the steps of preparing a semiconductor substrate and setting the semiconductor substrate in a reaction chamber, supplying an aluminum source material and NH3 gas into the reaction chamber simultaneously for being absorbed on the semiconductor substrate, discharging unreacted MTMA or by-product by flowing nitrogen gas into the reaction chamber or vacuum purging, supplying an oxygen source material into the reaction chamber for being absorbed on the semiconductor substrate, and discharging unreacted oxygen source or by-product by flowing nitrogen gas into the reaction chamber or vacuum purging.