Method of highly purifying Si surface and a atomically flattening method for an Si surface

Metal impurities, particularly, Ni as a transition metal under the Si surface which are mainly attributable to surface defects are removed to highly purify the Si surface, and the Si surface is atomically flattened correspondingly by hydrogenating the Si surface containing metal impurities under the surface by means of a gas phase process or a liquid phase process, thereby extracting the metal impurities onto the Si surface.