SEMICONDUCTOR DEVICE AND ELECTRONIC SYSTEM INCLUDING THE SAME

A semiconductor device may include a plurality of gate electrodes apart from each other in a vertical direction on a substrate; a plurality of channel structures penetrating the plurality of gate electrodes and extending in the vertical direction; and a plurality of bit lines arranged on and connected to the plurality of channel structures. The plurality of bit lines may include a plurality of lower bit lines and a plurality of upper bit lines at different vertical levels from each other to constitute at least two layers. The plurality of upper bit lines may be apart from each other in a first horizontal direction and extend in parallel with each other in a second horizontal direction perpendicular to the first horizontal direction. A lower expansion space may be defined between two lower bit lines adjacent to each other among the plurality of lower bit lines.