A method for manufacturing a semiconductor device including a first conductive type impurity region formed by introducing a first conductive type impurities in a first region of a semiconductor region and heating the first region, a second conductive type impurity region formed by introducing a second conductive type impurities in a second region of the semiconductor region and heating the second region, the method including covering the second region with a mask and then introducing the first conductive type impurities in a surface of the first region, removing the mask by a process using gas including oxygen while forming an oxide film on the surface of the first region by the processing using the gas including the oxygen, and introducing the second conductive type impurities in a surface of the second region by using the oxide film as a mask.