A wafer polishing apparatus includes one or more wafer carriers each containing one or more wafers mounted on both sides of the carrier. Upper and lower turntables having upper and lower polishing surfaces, rotate to polish the wafers attached to the carriers. Hence, wafers on the top of the carriers, and wafers on the bottom of the carriers are polished simultaneously. This configuration increases throughput; also, thermal deformations in the wafers are reduced, thus improving flatness.