NOVELTY - Bias power of direct current power and/or high frequency power of radio frequency (RF) are supplied together with high frequency power of very high frequency to discharge chamber (102). Direct current component of electric current flowing into bias electrode (113) is controlled, in terms of current density based on area of an inner wall of chamber (102).    USE - Process and apparatus for forming a semiconductor layer on a substrate especially a semiconductor layer of the non-monocrystalline silicon type such as amorphous silicon, amorphous silicon germanium, amorphous silicon carbide or amorphous silicon which is used in solar cells, photosensitive drums for photocopying machines, image sensors for facsimiles, thin film transistors for liquid crystal display devices etc..    ADVANTAGE - A good-quality semiconductor layer can be deposited over a large area at a high speed.    DETAILED DESCRIPTION - A process for manufacturing a semiconductor layer involves introducing a raw gas into a discharge chamber (102) and supplying high-frequency power to the chamber to decompose the raw gas by discharge, thereby forming a semiconductor layer on a substrate (107) within the chamber (102). The process comprises: (a) supply high frequency power of at least very high frequency; (b) supplying bias power of direct current power and/or high frequency power of radio frequency (RF) together with the high frequency power of VHF to chamber (102); and (c) controlling a direct current component of an electric current flowing into an electrode (113), to which bias power is supplied, to be 0.1 to 10 A/m2 in terms of a current density based on the area of an inner wall of the chamber (102).    INDEPENDENT CLAIMS are also included for the following:    (a) A process for producing a semiconductor layer which comprises: supplying high frequency power of VHF to at least two discharge chambers (102); supplying bias power of different levels from each other to the chambers, according to respective film-forming conditions in the chambers; and controlling the electric potential of each electrode (113) to which bias power is supplied, to the same level as that of the substrate (107) or positive potential against the substrate.    (b) A process for manufacturing a photovoltaic cell which comprises: supplying high-frequency power of at least VHF in the step of forming the i-type semiconductor layer; supplying bias of direct current power or RF together with the high frequency power of VHF to discharge chamber (102); and controlling a direct current component of an electric current flowing into an electrode (113) to which bias power is supplied, to be 0.1 to 10 A/m2 in terms of current density based on the area of an inner wall of the chamber (102).    (c) An apparatus for producing a semiconductor layer, the apparatus comprising: a means (105) for supplying high-frequency power of at least VHF; a means for supplying bias power of direct current power and/or high-frequency power of RF together with high frequency power of VHF to the discharge chamber (102); and a means for controlling direct current component of an electric current flowing into an electrode (113), to which bias power is supplied, to be 0.1 to 10 A/m2 in terms of a current density based on the area of an inner wall of the chamber (102).    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of the apparatus for forming a semiconductor layer.    Vacuum vessel (101)    Film forming chamber (discharge chamber) (102)    Gas inlet pipe (103)    Exhaust pipe (104)    High frequency power source (105)    Rod electrode (106)    Moving substrate (107)    Heater (109)    Direct current power source (110)    Ammeter (111)    Choke coil (112)    Bias electrode (113)