Three-dimensional semiconductor device

A three-dimensional (3D) semiconductor device comprising:

• a plurality of stack structures that extend in a first direction and that are spaced apart from each other in a second direction, each of the plurality of stack structures comprising electrodes that are vertically stacked on a substrate;
• first vertical channels and second vertical channels that penetrate each of the stack structures;
• a first horizontal channel that extends in the first direction under each of the stack structures, wherein the first horizontal channel connects the first vertical channels and the second vertical channels to each other;
• second horizontal channels that are in contact with both sidewalls of the first horizontal channel, wherein each of the second horizontal channels extends in the first direction and is between the stack structures that are adjacent one another when viewed from a plan view;
• a conductive line that extends in the first direction on each of the stack structures and that is connected to the second vertical channels;
• and
• a bit line that extends in the second direction on the conductive line and that is connected to the first vertical channels.