Abstract: A slurry contains MnO.sub.2 or other manganese oxide as a primary component of abrasive particles. Further, a polishing process using such a manganese oxide abrasive and a fabrication process of a semiconductor device using such a polishing process are disclosed.

Abstract: A fine particulate polishing agent comprises fine particles of a solid solution composed of single-crystal ceric oxide and silicon dioxide and fine particles of silicon dioxide. A slurry polishing agent comprising the fine particulate polishing agent can be prepared by a method which comprises the steps of mixing, with stirring, single-crystal ceric oxide fine particles, silica sol and a liquid; drying the mixture; subjecting the dried particulate material to a thermal treatment at a high temperature and then cooling the solid solution powder formed by the thermal treatment and composed of single crystal ceric oxide and silicon dioxide; again mixing the powder with silica sol and a liquid; and then subjecting the mixture to deagglomeration using a wet pulverizing mill to give a slurry.

Abstract: Cerium oxide ultrafine particles consist essentially of cerium oxide single crystal grains having a grain size ranging from 10 to 80 nm and the cerium oxide ultrafine particles can be prepared by a method which comprises the steps of mixing, with stirring, an aqueous solution of cerous nitrate with a base in such a mixing ratio that the pH value of the mixture ranges from 5 to 10, then rapidly heating the resulting mixture up to a temperature of 70 to 100.degree. C. and maturing the mixture at that temperature. The cerium oxide ultrafine particles not only have an average particle size ranging from 10 to 80 nm, but also are uniform in the particle size and in the shape.

Abstract: A fine particulate polishing agent is based on cerium oxide and silicon oxide; a slurry polishing agent comprises the foregoing fine particulate polishing agent which can be prepared by a method which comprises the steps of mixing, with stirring, cerium oxide fine particles, silica sol and a liquid; drying the mixture; mixing the material with a liquid; and then subjecting the mixture to deagglomeration using a wet pulverizing mill to give a slurry. Preferably, the dried particulate material is subjected to a thermal treatment at a high temperature of 150.degree. to 1200.degree. C., preferably 800.degree. to 900.degree. C., thereby to produce a solid solution of cerium oxide and silicon oxide. The slurry polishing agent can ensure the achievement of surface roughness comparable to or superior to that achieved by the colloidal silica polishing agents and a high polishing rate at least comparable to that achieved by the conventional cerium oxide polishing agents.