A semiconductor device 1 comprises a semiconductor substrate 2 having a through hole 3. A first insulation layer 4 having an opening 4a equal in diameter to the through hole 3 covers a front surface of the semiconductor substrate 2, and a first wiring layer 5 is formed thereon to cover the opening 4a. Further, a second insulation layer 6 is formed in the through hole 3 and on a rear surface of the semiconductor substrate 2. The second insulation layer 6 is formed to be in contact with an inner side of the first wiring layer 5 and has, in its contact portion, a plurality of small openings 6a smaller in diameter than the opening 4 of the first insulation layer 4. Further, a second wiring layer 7 is formed to fill the inside of the through hole 3, and the second wiring layer 7 is in contact with the inner side of the first wiring layer 5 via the small openings 6a of the second insulation layer 6.