Three-dimensional semiconductor device

A three-dimensional semiconductor device may comprise a first cell region, a second cell region, and a via plug region disposed between the first cell region and the second cell region; a word line stack disposed in the first cell region, the via plug region, and the second cell region, the word line stack including a plurality of word lines and a plurality of interlayer insulating layers which are alternately stacked; and a plurality of via plugs exclusively connected to the plurality of the word lines, respectively, by vertically penetrating through the word line stack in the via plug region. The via plugs may have an arrangement of a zigzag pattern in a row direction from a top view. The diameters of the via plugs may increase in the row direction.