Abstract: Aluminum oxide particles are provided that include primary particles each having a hexahedral shape and an aspect ratio of 1 to 5. The aluminum oxide particles preferably have an average primary particle size of 0.01 to 0.6 ?m. The aluminum oxide particles preferably have an alpha conversion rate of 5 to 70%. Further, the aluminum oxide particles preferably have an average secondary particle size of 0.01 to 2 ?m, and the value obtained by dividing the 90% particle size of the aluminum oxide particles by the 10% particle size of the aluminum oxide particles is preferably 3 or less. The aluminum oxide particles are used, for example, as abrasive grains in the applications of polishing semiconductor device substrates, hard disk substrates, or display substrates.

Abstract: A polishing composition is disclosed containing a nonionic active agent with a molecular weight of 1,000 or more and less than 100,000 and an HLB value of not less than 17, a basic compound, and water. The nonionic active agent is preferably an oxyalkylene homopolymer or a copolymer of different oxyalkylenes. The polishing composition may further contain at least one of silicon dioxide and a water-soluble polymer. The polishing composition is used, for example, in polishing the surface of semiconductor substrates such as silicon wafers.