Surface treatment apparatus

A surface treatment apparatus that performs film formation on a surface of a workpiece in a chamber, the surface treatment apparatus comprising:

• an electrode that is placed facing the workpiece and supplies reaction gas or releases target particles to the workpiece;
• a gas supply pipe that is installed along an outer periphery of a flat electrode surface of the electrode and has, along a longitudinal direction of the pipe, a plurality of gas ejection ports through which film-forming gas, or an inert gas or a reactive gas for performing sputtering is supplied to the electrode surface of the electrode;
• and
• a gas discharge unit that discharges residual gas after film formation is ended,
• wherein the plurality of gas ejection ports are arranged such that gas supplied from the gas supply pipe is uniformly distributed on the electrode surface of the electrode,
• wherein the gas supply pipe includes:
• a plurality of bolts penetrating from a wall surface of the gas supply pipe and each having a distal end with a tapered shape;
• a plurality of tapered holes formed in the wall surface of the gas supply pipe, the distal end of each bolt being arranged in the corresponding tapered hole;
• and
• a plurality of washers each arranged between the wall surface of the gas supply pipe and a bottom surface of a head portion of the corresponding bolt, and
• wherein a thickness of the washers are thicker downstream in the gas supply pipe whereby diameters of the plurality of gas ejection ports of the gas supply pipe are larger downstream in the gas supply pipe.