A vertical plasma processing apparatus for a semiconductor process includes an airtight auxiliary chamber defined by a casing having an insulative inner surface and integrated with a process container. The auxiliary chamber includes a plasma generation area extending over a length corresponding to a plurality of target substrates in a vertical direction. A partition plate having an insulative surface is located between a process field and the plasma generation. The partition plate includes a gas passage disposed over a length corresponding to the plurality of target substrates in a vertical direction. A process gas is exited while passing through the plasma generation area, and is then supplied through the gas passage to the process field.