Provided is a semiconductor device manufacturing method such that miniaturization of a parallel p-n layer can be achieved, and on-state resistance can be reduced. Firstly, deposition of an n−-type epitaxial layer, and formation of an n-type impurity region and p-type impurity region that form an n-type region and p-type region of a parallel p-n layer, are repeatedly carried out. Furthermore, an n−-type counter region is formed in the vicinity of the p-type impurity region in the uppermost n−-type epitaxial layer forming the parallel p-n layer. Next, an n−-type epitaxial layer is deposited on the n−-type epitaxial layer. Next, a MOS gate structure is formed in the n−-type epitaxial layer. At this time, when carrying out a p-type base region diffusion process, the n-type and p-type impurity regions are caused to diffuse, thereby forming the n-type region and p-type region of the parallel p-n layer.