A semiconductor device may include active patterns of pillar-shapes disposed on a substrate and spaced apart from each other in one direction; a gate electrode extending in the one direction and overlapped with sidewalls of the active patterns; a gate insulating layer disposed between the gate electrode and the active patterns; bit lines connected to bottom surfaces of respective active patterns; and/or capacitors connected to top surfaces of the respective active patterns. Each of the active patterns may have no p-type/n-type (PN) junctions. A semiconductor device may include a substrate; active patterns on the substrate that are spaced apart from each other; a gate electrode configured to overlap sidewalls of the active patterns; and/or gate insulating layers between the gate electrode and respective active patterns. The active patterns may be doped with dopants of a same conductivity type.