According to some embodiments, a semiconductor device includes a semiconductor substrate, a metal portion, a first insulating film, and a second insulating film. The semiconductor substrate has a through-hole extending from a first surface of the semiconductor substrate to a second surface thereof opposite to the first surface. The metal portion is formed in the through-hole. The first insulating film is provided on the second surface of the semiconductor substrate and on a side surface of the through-hole. The second insulating film has a dielectric constant of not more than 6.5 and is provided on a metal portion-side surface of the first insulating film on the side surface of the through-hole of the semiconductor substrate.