PURPOSE: To uniformly etch a wafer having a large area under low pressure and to reduce foreign matters by installing magnetic dipoles on the wall of a plasma generating chamber.

CONSTITUTION: Leads 8 are mounted on the periphery of a processing chamber 4, currents flowing reversely through the leads 8 form magnetic dipoles at the adjacent leads, and a magnetic field indicated by lines 11 of magnetic force is formed only in the vicinity of the wall of the chamber 4. Here, the distribution of the magnetic field in the chamber 4 is strong in the vicinity of the wall face and abruptly weakened toward its center. As a result, diffusion of a plasma to the wall face is prevented by the magnetic field, and since the magnetic field at the center is weak, the plasma is sufficiently diffused. Thus, the plasma is confined to reduce its loss, and a high density plasma can be maintained even under low pressure to make the plasma density uniform. In the case of etching, a wafer having a large area can uniformly be etched.