A semiconductor device of an embodiment includes: a substrate; a first catalytic metal film on the substrate; graphene on the first catalytic metal film; an interlayer insulating film on the graphene; a contact hole penetrating through the interlayer insulating film; a conductive film at the bottom portion of the contact hole, the conductive film being electrically connected to the graphene; a second catalytic metal film on the conductive film, the second catalytic metal film being subjected to plasma processing with at least one kind of gas selected from hydrogen, nitrogen, ammonia, and rare gas; and carbon nanotubes on the second catalytic metal film.