A method for improving the quality of a SiC layer by effectively reducing or eliminating the carrier trapping centers by high temperature annealing and a SiC semiconductor device fabricated by the method. The method for improving the quality of a SiC layer by eliminating or reducing some carrier trapping centers includes the steps of: (a) carrying out ion implantation of carbon atom interstitials (C), silicon atoms, hydrogen atoms, or helium atoms into a shallow surface layer (A) of the starting SiC crystal layer (E) to introduce excess carbon interstitials into the implanted surface layer, and (b) heating the layer for making the carbon interstitials (C) to diffuse out from the implanted surface layer (A) into a bulk layer (E) and for making the electrically active point defects in the bulk layer inactive. After the above steps, the surface layer (A) can be etched or mechanically removed. The SiC semiconductor device is fabricated by the method.