In this article, the correlation of surface morphological defects and barrier-height inhomogeneities with the electrical characteristics of defective 4H-SiC Schottky barrier diodes (SBDs) before and after chemical-mechanical polishing (CMP) is investigated. The forward characteristics, an ideality factor and a single barrier height of a SBD, remain the same after CMP, so that CMP does not affect SBD characteristics. Most barrier-height inhomogeneities are eliminated or improved after CMP. Therefore, leakage current induced by barrier-height inhomogeneities are improved by CMP as well. In addition, about 40% of SBDs with carrots inside the active areas exhibits double barriers before CMP. This excludes that carrots are a cause of barrier-height inhomogeneities. In reverse-bias mode, CMP reduces reverse leakage current at low bias and increases breakdown voltage due to the reduction of thermionic field emission and elimination of local enhanced electric fields.