An ion implantation method is provided, which is able to improve the controllability of implanted dopant ions and the uniformity in concentration and profile of implanted dopant ions. A semiconductor substrate with a (100)-oriented crystal surface is prepared. An elongated mask with a specific pattern is formed on the surface of the substrate. A beam of dopant ions is irradiated to the surface of the substrate along a first direction, thereby selectively implanting the dopant ions into the substrate using the mask. The first direction has a first angle with a normal of the surface of the substrate in a plane perpendicular to a longitudinal axis of the mask, where the first angle is in the range from 7.degree. C. to 60.degree. C. The first direction has a second angle with a lateral axis of the mask in a plane parallel to the surface of the substrate, where the second angle is in the range from 5.degree. C. to 20.degree. C. The longitudinal axis of the mask is parallel to one of the -directions or one of the -directions.