A method for manufacturing a SiC semiconductor device comprising: forming an impurity layer (3, 4) in a SiC semiconductor layer (2, 5); and forming an oxide film on a surface of the SiC semiconductor layer (2, 5), wherein the forming the impurity layer (3, 4) includes: implanting an impurity in the SiC semiconductor layer (2, 5); applying a cap layer made of organic solvent on the surface of the SiC semiconductor layer (2, 5); annealing the cap layer to evaporate the organic solvent so that the cap layer is carbonized and transformed to a carbon layer; annealing the SiC semiconductor layer (2, 5) to activate the impurity in the SiC semiconductor layer (2, 5) under a condition that the surface of the SiC semiconductor layer (2, 5) is covered with the carbon layer; and removing the carbon layer, the forming the oxide film is performed after the removing the carbon layer, and wherein the annealing the SiC semiconductor layer (2, 5) includes: a first increasing of a temperature of the SiC semiconductor layer (2, 5) from a second temperature to a first temperature within a first time duration; and a first decreasing of the temperature of the SiC semiconductor layer (2, 5) from the first temperature to the second temperature within a second time duration, the first temperature is 2000°C, and the second temperature is 1600°C, and the first time duration is equal to or smaller than one minute, and the second time duration is equal to or smaller than one minute, wherein annealing the SiC semiconductor layer (2, 5) further includes: annealing the SiC semiconductor layer (2, 5) at the second temperature for a third time duration equal to or greater than thirty minutes, and wherein the first increasing of the temperature of the SiC semiconductor layer (2, 5) and the first decreasing of the temperature of the SiC semiconductor layer (2, 5) are performed during the annealing for a third time duration. forming an impurity layer (3, 4) in a SiC semiconductor layer (2, 5); and forming an oxide film on a surface of the SiC semiconductor layer (2, 5), wherein the forming the impurity layer (3, 4) includes: implanting an impurity in the SiC semiconductor layer (2, 5); applying a cap layer made of organic solvent on the surface of the SiC semiconductor layer (2, 5); annealing the cap layer to evaporate the organic solvent so that the cap layer is carbonized and transformed to a carbon layer; annealing the SiC semiconductor layer (2, 5) to activate the impurity in the SiC semiconductor layer (2, 5) under a condition that the surface of the SiC semiconductor layer (2, 5) is covered with the carbon layer; and removing the carbon layer, the forming the oxide film is performed after the removing the carbon layer, and wherein the annealing the SiC semiconductor layer (2, 5) includes: implanting an impurity in the SiC semiconductor layer (2, 5); applying a cap layer made of organic solvent on the surface of the SiC semiconductor layer (2, 5); annealing the cap layer to evaporate the organic solvent so that the cap layer is carbonized and transformed to a carbon layer; annealing the SiC semiconductor layer (2, 5) to activate the impurity in the SiC semiconductor layer (2, 5) under a condition that the surface of the SiC semiconductor layer (2, 5) is covered with the carbon layer; and removing the carbon layer, the forming the oxide film is performed after the removing the carbon layer, and wherein the annealing the SiC semiconductor layer (2, 5) includes: a first increasing of a temperature of the SiC semiconductor layer (2, 5) from a second temperature to a first temperature within a first time duration; and a first decreasing of the temperature of the SiC semiconductor layer (2, 5) from the first temperature to the second temperature within a second time duration, the first temperature is 2000°C, and the second temperature is 1600°C, and the first time duration is equal to or smaller than one minute, and the second time duration is equal to or smaller than one minute, wherein annealing the SiC semiconductor layer (2, 5) further includes: annealing the SiC semiconductor layer (2, 5) at the second temperature for a third time duration equal to or greater than thirty minutes, and wherein the first increasing of the temperature of the SiC semiconductor layer (2, 5) and the first decreasing of the temperature of the SiC semiconductor layer (2, 5) are performed during the annealing for a third time duration. annealing the SiC semiconductor layer (2, 5) at the second temperature for a third time duration equal to or greater than thirty minutes, and wherein the first increasing of the temperature of the SiC semiconductor layer (2, 5) and the first decreasing of the temperature of the SiC semiconductor layer (2, 5) are performed during the annealing for a third time duration.