It the substrate has an upper surface of SiO2 (or other bonding material), one can polish that surface without depositing another SiO2 layer, assuming that the upper surface of SiO2 has sufficient thickness to obtain a sufficient surface roughness and planarity with, e.g., CMP. EXAMPLE [0067] This example uses the case of attachment of a diamond substrate to a material such as GaAs, InP, or GaN wh