at the upper portion of the inner chamber 13 a gas shower electrode 14 as an upper electrode is arranged to the gas shower electrode 14 a first gas supply mechanism for supplying hydrogen gas and a second gas supply mechanism for supplying oso 4 gas are connected the first gas supply mechanism has a hydrogen gas supply source 29 and to the hydrogen gas supply source 29 one end of a pipe 18 is connected to the other end of the pipe 18 one end of a bulb 24 is connected and to the other end of the bulb 24 one end of a pipe 17 is connected to the other end of the pipe 17 one end of a mass flow controller mfc 27 is connected and to the other end of the mass flow controller 27 one end of a pipe 16 is connected to the other end of the pipe 16 one end of a bulb 23 is connected and to the other end of the bulb 23 one end of a pipe 15 is connected to the other end of the pipe 15 the gas shower electrode 14 is connected the second gas supply mechanism has an oso 4 gas supply source 30 and to the oso 4 gas supply source 30 one end of a pipe 22 is connected to the other end of the pipe 22 one end of a bulb 26 is connected and to the other end of the bulb 26 one end of a pipe.