Abstract: To provide a yttria sintered body having an excellent corrosion resistance to halogen-based corrosive gases and plasma and an excellent thermal shock resistance, and adapted for use as a component member in manufacturing apparatuses for semiconductor and liquid crystal devices, particularly in a plasma process apparatus. A yttria sintered body including tungsten of an average particle size of 3 ?m or less dispersed in the yttria so that a ratio of the tungsten relative to the yttria is ranging from 1 to 50% in terms of weight, and having an open pore rate of 0.2% or less and a thermal shock resistance by water submersion method of 200° C. or larger.

Abstract: To provide an inexpensive gas dispersion plate having a high corrosion resistance to halogen-based corrosive gasses and a plasma thereof, and capable of preventing particle generation from the gas hole, thereby contributing to an improvement in the production yield of the semiconductor devices. The gas dispersion plate includes one or plural gas holes in a base material formed by a Y2O3 ceramic material having a relative density of 96% or more, in which an edge part of the gas hole is formed by a sand blasting process into a rounded shape with a radius of curvature of 0.2 mm or more.

Abstract: To provide a yttria sintered body having an excellent corrosion resistance to halogen-based corrosive gases and plasma and an excellent thermal shock resistance, and adapted for use as a component member in manufacturing apparatuses for semiconductor and liquid crystal devices, particularly in a plasma process apparatus. A yttria sintered body including tungsten of an average particle size of 3 ?m or less dispersed in the yttria so that a ratio of the tungsten relative to the yttria is ranging from 1 to 50% in terms of weight, and having an open pore rate of 0.2% or less and a thermal shock resistance by water submersion method of 200° C. or larger.

Abstract: A gas diffusion plate has an alumina or an aluminum base material provided with one or more through holes and an yttria body shrink-fitted to one of the through holes and provided with one or more gas discharge holes.

Abstract: A plasma-resistant member used in a reaction chamber of a plasma treating apparatus is formed of a dense alumina sintered product having an average grain size of 18-45 &mgr;m, a surface roughness Ra of 0.8-3.0 &mgr;m and a bulk density of 3.90 g/cm3 or over.