A semiconductor device has a plurality of vertical channels extending upright on a substrate, a plurality of bit lines extending among the vertical channels, a plurality of word lines which include a plurality of gates disposed adjacent first sides of the vertical channels, respectively, and a plurality of conductive elements disposed adjacent second sides of the vertical channels opposite the first sides. The conductive elements can provide a path to the substrate for charge carriers which have accumulated in the associated vertical channel to thereby mitigate a so-called floating effect.