A semiconductor device may include first and second sub chips stacked sequentially and a through contact electrically connecting the first and second sub chips to each other. Each of the first and second sub chips may include a substrate and a plurality of interconnection lines, which are interposed between the substrates. The interconnection lines of the second sub chip may include first and second interconnection lines having first and second openings, respectively, which are horizontally offset from each other. The through contact may be extended from the substrate of the second sub chip toward the first sub chip and may include an auxiliary contact, which is extended toward the first sub chip through the first and second openings and has a bottom surface higher than a top surface of the uppermost one of the interconnection lines of the first sub chip.