A semiconductor device includes a first gate pattern and a second gate pattern on a substrate, the first gate pattern having a first height and the second gate pattern having a second height, an insulating pattern on the substrate covering the first and second gate patterns, the insulating pattern including a trench exposing the substrate between the first and second gate patterns, a spacer contacting at least a portion of a sidewall of the insulating pattern within the trench, the spacer spaced apart from the first and second gate patterns and having a third height larger than the first and second heights, and a contact structure filling the trench.