A molding is formed by laminating an aggregate of SiC and a paste containing Si and C powders on an epitaxial layer of SiC formed on a support substrate of SiC to form an intermediate sintered body in which polycrystalline SiC is produced from the Si and C powders by reaction sintering, free Si is carbonized to SiC to form a sintered body layer, and the support substrate is removed from the epitaxial layer to form a semiconductor substrate in which the epitaxial layer and the sintered body layer are laminated.