Abstract: In a plasma processing apparatus for generating a plasma in a plasma generation space between a lower electrode and an upper electrode so that a processing object mounted on the lower electrode is subjected to plasma processing, a plurality of cutout portions for absorption of strain caused by thermal expansion due to rapid temperature increases in the plasma processing are formed at an equal pitch in an outer edge portion of a gas shower plate included in the upper electrode. Thus, the gas shower plate can be prevented from being damaged by occurrence of cracks in the outer edge portion of the gas shower plate or the like.

Abstract: In a plasma processing apparatus for generating a plasma in a plasma generation space between a lower electrode and an upper electrode so that a processing object mounted on the lower electrode is subjected to plasma processing, a plurality of cutout portions for absorption of strain caused by thermal expansion due to rapid temperature increases in the plasma processing are formed at an equal pitch in an outer edge portion of a gas shower plate included in the upper electrode. Thus, the gas shower plate can be prevented from being damaged by occurrence of cracks in the outer edge portion of the gas shower plate or the like.

Abstract: In a plasma treating apparatus, a ceramic porous substance having a three-dimensional network structure in which a frame portion formed of ceramic containing alumina is provided continuously like a three-dimensional network is used for the material of an electrode member for the plasma treating apparatus to be attached to the front surface of a gas supplying port of an electrode for plasma generation, and a gas for plasma generation is caused to pass through a hole portion formed irregularly in the three-dimensional network structure. Consequently, the distribution of the gas to be supplied is made uniform to prevent an abnormal discharge so that uniform etching having no variation can be carried out.

Abstract: In a plasma treating apparatus, a ceramic porous substance having a three-dimensional network structure in which a frame portion formed of ceramic containing alumina is provided continuously like a three-dimensional network is used for the material of an electrode member for the plasma treating apparatus to be attached to the front surface of a gas supplying port of an electrode for plasma generation, and a gas for plasma generation is caused to pass through a hole portion formed irregularly in the three-dimensional network structure. Consequently, the distribution of the gas to be supplied is made uniform to prevent an abnormal discharge so that uniform etching having no variation can be carried out.

Abstract: After sintering, ceramic body of Si.sub.3 N.sub.4 -SiC is heat-treated at 500.degree.-1500.degree. C. in atmosphere of gas mixture of chlorine and nitrogen whereby SiC is converted into silicon chloride which in turn is nitrided to form Si.sub.3 N.sub.4 in the pores of the ceramic body to provide closed pore structure. Gas mixture may contain oxygen. Heat treatment may be conducted in pressurized atmosphere of gas mixture.