Abstract: A semiconductor-device-producing substrate and method for producing the substrate which is inexpensive and good in quality and which has a large-area surface layer. A photoelectric conversion device and method uses the semiconductor-device-producing substrate, with high efficiency being obtained by means of the large-area light-receiving surface and three-dimensional structure of the photoelectric conversion device. Semiconductor granular crystals are arranged in at least one layer on a semiconductor substrate and connected and fixed to one another by heating or by a chemical vapor-phase deposition method to thereby form a semiconductor-device-producing substrate. An active layer of one conduction type is formed on the substrate and then another active layer of the other conduction type is formed on the surface of the first-mentioned active layer by a chemical vapor-phase deposition method or by a diffusion method to thereby form a PN junction surface having a three-dimensional structure.