A semiconductor device comprising a first insulation layer, a second insulation layer, a first barrier film, a second barrier film, a diffusion layer. The device further comprises an upper contact hole, a lower contact hole, and a contact plug. The upper contact hole penetrates the second insulation layer and has a bottom in the second barrier film. The bottom has a width greater than a trench made in the first insulation layer, as measured in a direction crossing the widthwise direction of the trench. The lower contact hole penetrates the first insulation layer and first barrier film, communicates with the first contact hole via the trench and is provided on the diffusion layer. The upper portion of the lower contact hole has the same width as the trench. The contact plug is provided in the upper contact hole and lower contact hole.