A semiconductor fabricating unit used for the photochemical vapor phase growth process in which a first reaction gas decomposed by excitation with a laser beam is reacted with a second reaction gas turned into plasma by a plasma generator in a reaction chamber where a substrate is placed, so that a variety of layers are formed on the substrate at a low temperature. In the reaction chamber are further provided upper and lower electrodes that are opposed to each other. The electrode on the upper side is connected to an r-f power source and the electrode on the lower side is used as the common electrode on which the substrate is mounted, thereby controlling the rate of forming the layer. Further, a source of ultraviolet rays is provided to irradiate the interior of the reaction chamber with ultraviolet rays so that a dense layer can be formed.
