A semiconductor device includes a substrate having a field area that defines active areas, gate trenches in the substrate and extending in a first direction, a buried gate in a respective gate trench, gate capping fences in a respective gate trench over a respective buried gate, the gate capping fences protruding from top surfaces of the active areas and extending in the first direction, bit line trenches in the gate capping fences, a respective bit line trench crossing the gate capping fences and extending in a second direction perpendicular to the first direction, an insulator structure on inner walls of a respective bit line trench, bit lines and bit line capping patterns stacked on the insulator structures in a respective bit line trench, contact pads self-aligned with the gate capping fences and on the substrate between the adjacent bit lines, and a lower electrode of a capacitor on a respective contact pad.