Plasma processing apparatus

An apparatus for a plasma processing comprising:

• at least one annular member, each having at least one groove or at least one protrusion formed along a circumferential direction on a bottom surface of the annular member, the groove or the protrusion having a first thread formed on a side surface thereof along the circumferential direction;
• a support unit having at least one protrusion or at least one groove formed along the circumferential direction on a placing surface on which the annular member is placed such that the groove or the protrusion of the annular member is fitted with the protrusion or the groove of the support unit, the protrusion or the groove of the support unit having a second thread formed on a side surface thereof along the circumferential direction;
• a chamber in which the support unit is disposed;
• and
• a pressure control unit configured to control a pressure in the chamber such that a driving force rotating the annular member in the circumferential direction is obtained.