Some embodiments relate to a carrier head. The carrier head includes a housing configured to enclose a wafer, wherein the housing includes a retaining ring recess configured to circumferentially surround the wafer. A retaining ring, which includes a first ring-shaped layer and a second ring-shaped layer, is disposed in the retaining ring recess. The second ring-shaped layer is disposed deeper in the retaining ring recess than the first ring-shaped layer and separates the first ring-shaped layer from a bottom of the retaining ring recess. A hardness of the second ring-shaped layer is less than a hardness of the first ring-shaped layer.