Polycrystalline 3C-SiC films are etched by oxygen-mixed sulfur hexafluoride transformer coupled plasmas for microelectromechanical systems (MEMS) applications. Silicon dioxide is employed as etching masks. which avoids the micromasking phenomena and chamber contamination commonly involved when using metals as masks. The etch rate, selectivity, and profile are characterized as functions of O-2 percentage in the etching gas. Etch rates of SiC remain almost unchanged at about 3600 Angstrom/min up to 50% O-2, but decrease significantly when more than 50% 02 is used. Etch selectivity of SiC over SiO2 reaches maximum of 2.6 when using 50% O-2. The chemical composition and the topography of the etched SiC films are also examined. By integrating the etching process with conventional surface micromachining technology, functional SiC-based MEMS resonators are fabricated. (C) 2004 American Vacuum Society.