Method for manufacturing insulated gate type switching device having low-density body region and high-density body region

1. A method of manufacturing an insulated gate type switching device, the method comprising:

implanting second conductivity type impurities into a surface of a semiconductor substrate including a first region of a first conductivity type so as to form a second region of a second conductivity type in a range in the semiconductor substrate that is exposed on the surface;

forming a third region of the second conductivity type on the surface by epitaxial growth after the formation of the second region, the third region having a second conductivity type impurity density lower than a second conductivity type impurity density in the second region and the third region having a first conductivity type impurity density lower than a first conductivity type impurity density in the first region;

forming a fourth region of the first conductivity type being in contact with the third region and separated from the first region by the second and third regions; and

forming a trench gate electrode facing the second and third regions via an insulating film.