Plasma processing apparatus

A plasma processing apparatus comprising:

• a processing container in which a plasma processing is performed on a substrate to be processed;
• a holding stage which is disposed in the processing container and holds thereon the substrate to be processed;
• a microwave generator which generates a microwave for exciting plasma;
• a dielectric plate which is provided at a location facing the holding stage and transmits a microwave into the processing container, the dielectric plate having a bottom surface facing the holding stage;
• a base housing portion, which penetrates an upper portion of the dielectric plate in a plate vertical thickness direction;
• and
• a reactive gas supply unit which supplies a reactive gas for plasma processing toward a central region of the substrate to be processed held by the holding stage,
• wherein the reactive gas supply unit includes an injector base, which is housed inside the base housing portion, and has a wall surface exposed to the inside of the processing container and directly open toward the holding stage and a supply hole formed in the wall surface, a reactive gas being supplied into the processing container through the supply hole, the wall surface and the supply hole being positioned vertically above the bottom surface of the dielectric plate, and
• a seal provided between an inner wall of the base housing portion and the wall surface of the injector base.