Semiconductor devices capable of a sensing margin of a semiconductor device are described. A semiconductor device may include a plurality of mats, a plurality of sensing circuits, a plurality of connecting circuits, and a plurality of mat dividing circuits. The mats are divided into upper regions and lower regions and activated by word lines. The sensing circuits are arranged in regions among the plurality of mats and are configured to sense/amplify data applied from the plurality of mats. The connecting circuits are configured to control connections between the mats and the sensing circuits in correspondence to a plurality of bit line selection signals. The mat dividing circuits are configured to selectively connect bit lines of the upper regions and the lower regions to each other in correspondence to a plurality of mat selection signals.