A semiconductor device includes front and back side structures on first and second surfaces of a substrate, respectively, and first and second through electrodes penetrating the substrate. The front side structure includes a circuit device, a first front side conductive pattern at a first level, a second front side conductive pattern at a second level, a lower insulating structure, and first to third insulating structures. The back side structure includes a first and a second back side conductive pattern on the same level. The first through electrode contacts the first back side conductive pattern and the first front side conductive pattern. The second through electrode contacts the second back side conductive pattern and the second front side conductive pattern. The first front side conductive pattern penetrates the second insulating structure and at least a portion of the third insulating structure.