PURPOSE: To freely control an impurity profile by simultaneously diffusing two or more sorts of impurities which are the same conductive type but have different diffusion coefficient from the same region of a semiconductor.

CONSTITUTION: After a thermal oxide film 2 is formed on an n-type Si substrate 1, patterned for impurity diffusion and is implanted with phosphorus ions. Then, the above-mentioned same position is implanted with antimony ions. Then, annealed and later, an impurity is diffused at a required temperature and an n-type impurity diffusion layer 3 is formed in the n-type Si substrate 1. In the above-mentioned process, the profile of impurity diffusion can be varied with one diffusion by changing the quantity of ion implantation, the time of diffusion, etc.