A semiconductor device is provided. The semiconductor device includes a first insulating interlayer disposed on a first surface of a substrate; a pad pattern disposed on a lower surface of the first insulating interlayer, the pad pattern including a first copper pattern; and a through silicon via passing through the substrate and the first insulating interlayer, and contacting the first copper pattern of the pad pattern. The through silicon via includes a first portion passing through the substrate and the first insulating interlayer, and a second portion under the first portion and extending to a portion of the first copper pattern in the pad pattern. A boundary of the through silicon via has a bent portion between the first portion and the second portion.