A method of manufacturing a semiconductor device includes: (A) a wafer process; and (B) a bias application process after the wafer process. The wafer process includes: (a) forming a n-type well in a p-type semiconductor substrate; (b) forming a p-type well in the n-type well; and (c) forming a transistor on the p-type well, the transistor having a n-type source/drain diffusion layer. In the bias application process, a forward bias is applied between the p-type well and the n-type well to move heavy metal ions.