NOVELTY - The method involves performing oxidation film formation process for oxidizing surface of a semiconductor substrate and forming an oxide film. Oxide-film removal process is performed for removing the oxide film, where sum amount of metal impurity (2) is adjusted in surface (1) of the semiconductor substrate more than 1x 109 atoms/cm2 and below 1x 1014 atoms/cm2. Multiple pits are formed on surface of the semiconductor substrate by wet-etching the surface of the semiconductor substrate by using a catalyst in order to adjust the metal impurity on surface of the semiconductor substrate.    USE - Method for modifying or reforming semiconductor substrate by removing impurities from surface of semiconductor substrate, e.g. solar cell wafer.    ADVANTAGE - The method involves performing oxidation film formation process for oxidizing surface of a semiconductor substrate and forming an oxide film. Oxide-film removal process is performed for removing the oxide film, and hence removes internal metal impurities from surface of a semiconductor substrate to provide highly pure semiconductor substrate.    DETAILED DESCRIPTION - The method involves performing oxidation film formation process for oxidizing surface of a semiconductor substrate and forming an oxide film. Oxide-film removal process is performed for removing the oxide film, where sum amount of metal impurity is adjusted in surface of the semiconductor substrate more than 1x 109 atoms/cm2 and below 1x 1014 atoms/cm2. Multiple pits are formed on surface of the semiconductor substrate by wet-etching the surface of the semiconductor substrate by using a catalyst in order to adjust the metal impurity on surface of the semiconductor substrate. Impurity is diffused inside the semiconductor substrate with bringing the impurities together in the surface vicinity of the semiconductor substrate. Impurities are removed from the surface.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a solar cell wafer.    Surface (1)    Impurity (2)    Inside of solar cell wafer (3)    Damage layer (4)    Solar cell wafer (5)