A method for manufacturing a SiC semiconductor device includes: forming an impurity layer in a SiC layer; and forming an oxide film on the SiC layer. The forming the impurity layer includes: implanting an impurity in the SiC layer; applying a cap layer on the SiC layer; annealing the cap layer to be transformed to a carbon layer; annealing the SiC layer to activate the impurity with covering the SiC layer with the carbon layer; removing the carbon layer; and performing a sacrifice oxidation process. The performing the sacrifice oxidation process includes: forming a sacrifice oxide film; and removing the sacrifice oxide film. The forming the oxide film is performed after the performing the sacrifice oxidation process.