Plasma processing method

A plasma processing method comprising:

• a first step of disposing a wafer to be processed in a processing chamber depressurized in a vacuum container and introducing into the processing chamber a gas having reactivity with a film to be processed disposed in advance on a top surface of the wafer to form an adhesion layer on the film;
• a second step of expelling a part of the gas having reactivity which remains in the processing chamber while supply of the gas having reactivity is stopped;
• a third step of introducing a rare gas into the processing chamber to form a plasma in the processing chamber and desorbing reaction products of the adhesion layer and the film to be processed from the wafer using particles in the plasma and vacuum ultraviolet light generated from the plasma;
• and
• a fourth step of expelling the reaction products from the processing chamber while the plasma is not formed.