SnO$_2$ is one of the most suitable gas sensor materials. The microstructure and surface morphology of films must be controlled because the electrical and optical properties of SnO$_2$ films depend on these characteristics. The effects of chemical mechanical polishing(CMP) on the variation of morphology of SnO$_2$ films prepared by RF sputtering system were investigated. The commercially developed ceria-based oxide slurry, silica-based oxide slurry, and alumina-based tungsten slurry were used as CMP slurry. Non-uniformities of all slurries met stability standards of less than 5 %. Silica slurry had the highest removal rate among three different slurries, sufficient thin film topographies and suitable root mean square(RMS) values.