SEMICONDUCTOR DEVICES HAVING GATE STRUCTURES

A semiconductor device includes a substrate having a plurality of active regions and defining a plurality of first gate trenches and a plurality of second gate trenches crossing the plurality of active regions and extending in a first horizontal direction, a plurality of gate structures including a plurality of first gate structures within the plurality of first gate trenches and a plurality of second gate structures within the plurality of second gate trenches, a bit line structure crossing the plurality of gate structures and extending in a second horizontal direction that intersects the first horizontal direction, and a contact plug disposed on a side surface of the bit line structure. When viewed in plan view, an area of at least some of the plurality of first gate structures is different from an area of at least some of the plurality of second gate structures.