A semiconductor device, including a substrate having an active region defined therein, a plurality of bit lines extending on the substrate in a first direction, a plurality of interconnection lines extending on the substrate in a second direction, a pad electrically connected to the plurality of interconnection lines and configured to apply an external voltage, a plurality of metal contacts electrically connecting the interconnection lines and the plurality of bit lines, and a plurality of bit line contacts that are in contact with the active region and electrically connect the plurality of bit lines and the active region, wherein a size of at least some of the bit line contacts and/or at least some of the metal contacts vary based on a distance of the respective bit line contact or the metal contact from the pad.