To reduce power consumption, and to reduce generation of noise when carrying out the surface treatment of a semiconductor substrate which is placed on the upper face of a lower electrode disc with plasma in a chamber.

In this processor, a lower electrode disc 5 is constituted of a metal electrode body 7 with high thermal conductivity positioned on the uppermost face, a heating body 9 incorporating a heater 8, and an insulator 10 with high thermal conductivity interposed between them. High frequency is impressed via conductor wiring 23 put through the insulator to the electrode body 7, and the lower electrode disc 5 is supported by a support body 11 fixed to the lower face of the heating body 9.