Catalyst-referred etching (CARE) is an abrasive-free planarization method. We used 3-inch and 2-inch 4H-SiC (0001) 4° off-axis substrates to investigate the processing characteristics that are affected by the substrate diameter. The surface roughness of the 3-inch substrate was extremely smooth over the whole substrate. The surface roughness and removal rate of the 3-inch substrate were approximately the same as those of the 2-inch substrate.