A semiconductor producing apparatus for use in photochemical vapor deposition for forming various types of film on a substrate at a low temperature as a first reaction gas excited and decomposed by a laser beam and a second reaction gas converted into a plasma state by a plasma generator react with each other in a reaction chamber in which a substrate is mounted. Two kinds of electrodes are provided in upper and lower positions in the reaction chamber opposing each other. The upper electrode is connected to a high-frequency power source and the lower electrode is used as a common electrode on which the substrate is mounted to control film forming speed, while an ultraviolet light source for irradiating the interior of the reaction chamber with ultraviolet rays is provided to obtain a dense film.