A lower concentration impurity diffusion region can be formed under excellent control, even when a low heat-resistant substrate is used. At the time of doping a semiconductor layer, a mask such as sidewalls (24) where an energy beam passes through, is formed on a part of a surface of a semiconductor layer (21), dopant ions (25) are adsorbed on the surface of the semiconductor layer (21) except a region in which the mask is formed, and an energy beam EBL is irradiated onto the semiconductor layer (21) having the formed mask to introduce the dopant ions into the semiconductor layer (21). In the lower part of the mask such sidewalls (24), diffusion in transverse direction occurs and lower concentration impurity diffusion regions can be formed in excellent reproducibility under excellent control.