The electron cyclotron resonance (ECR) etching of silicon carbide (SiC) was studied using SF 6 +O 2 based plasma. The role of O 2 was studied by varying the O 2 flow rate while keeping the total gas flow constant. It was found that oxygen enhances the etch rate at low O 2 fraction through releasing more fluorine atoms, while lowers the etch rate at high O 2 fraction by diluting fluorine atoms and forming an oxide-like layer. The etched surface roughness was found to be affected by the surface oxidation and oxygen ion related physical ion bombardment. The role of oxygen in chemical etching of carbon was found to be insignificant. In general, the etched surface is smooth and free of micromasking effect that can arise from Al contamination and C rich layer.