Method of manufacturing a semiconductor device including pre-oxidation process

A method for manufacturing a semiconductor device can reduce a micro-roughness and does not change a construction and electric characteristics of elements formed in the semiconductor device. In the method for manufacturing the semiconductor device including a pre-oxidation process in which an oxide layer is first formed on a silicon wafer, and the oxide layer is secondly eliminated to eliminate impurities on a surface of the silicon wafer, a formation of the oxide layer in the pre-oxidation process is performed in an oxidization atmosphere including H2O and gas including germanium hydride (german -GeH4-). Since german (GeH4) is included in the oxidization atmosphere, it is possible to reduce a softening temperature of the silicon dioxide formed in pre-oxidation, thereby decreasing the micro-roughness on the surface of the silicon wafer. Furthermore, since it is possible to perform the pre-oxidation process in a low temperature and in a short time, there is no change of a construction and electric characteristics of elements formed in the semiconductor device.