Abstract: A semiconductor device includes: an insulated gate electrode structure provided in a semiconductor substrate; a base region; a first main electrode region; a contact plug buried in a trench penetrating the first main electrode region to reach the base region with a barrier metal film interposed; an interlayer insulating film provided with a contact hole integrally connected to the trench; a contact region provided in contact with a bottom of the trench; and a second main electrode region, wherein an opening width at a lower end of the contact hole conforms to a width at an opening of the trench, an upper part of a side wall continued from the opening of the trench has a curved surface convex to an outside, and a lower part of the side wall continuously connected to the bottom of the trench has a curved surface convex to the outside.