Reactive-species supply device and surface treatment apparatus

A reactive-species supply device configured to supply a treatment gas to an electric discharge space that is formed by at least one pair of electrodes, for thereby supplying at least a reactive species formed in a plasma, to an object through a reactive-species output port, said reactive-species supply device comprising:

• a reactive-species outlet passage disposed between said electric discharge space and said reactive-species output port;
• and
• an earth ground member disposed in a portion of said reactive-species outlet passage, said portion of said reactive-species outlet passage being distant, by a given distance, from said reactive-species output port,
• wherein said reactive-species outlet passage has (a) a main passage communicating said electric discharge space and said reactive-species output port and (b) a branch passage connected to said main passage,
• and wherein said earth ground member is provided to close said branch passage.