A semiconductor device includes a substrate including first and second region, a bit line structure on the first region, key structures on the second region, each key structure having an upper surface substantially coplanar with an upper surface of the bit line structure, a first trench disposed between two adjacent key structures spaced apart from each other in a first direction, a filling pattern in a lower portion of the first trench, the filling pattern having a flat upper surface and including a first conductive material, and a first conductive structure on the flat upper surface of the filling pattern, an upper sidewall of the first trench, and the upper surface of each of the plurality of key structures, the first conductive structure including a second conductive material.