A chemical-mechanical polishing process using a silicon oxynitride anti-reflection layer (S340) includes: (S1) providing a semiconductor wafer comprising a substrate (S310), an oxidation layer (S320) formed on the substrate (S310), a silicon nitride layer (S330) formed on the oxidation layer (S320), an anti-reflection layer (S340) formed on the silicon nitride layer (S330), a trench extending through the anti-reflection layer (S340) and into the substrate (S310), and a first silicon dioxide layer (S350) filling the trench and covering the anti-reflection layer (S340); (S2) polishing the first silicon dioxide layer (S350) until the anti-reflection layer (S340) is exposed; (S3) removing the anti-reflection layer (S340) by dry etching; (S4) forming a second silicon dioxide layer (S360) on the surface of the semiconductor wafer from which the anti-reflection layer (S340) is removed; (S5) polishing the second silicon dioxide layer (S360) until the silicon nitride layer (S330) is exposed; (S6) and, removing the silicon nitride layer (S330).