An embodiment of a semiconductor device includes a substrate including a cell region and a peripheral region; a cell gate pattern on the cell region; and a peripheral gate pattern on the peripheral region, wherein a first cell insulation layer, a second cell insulation layer, and a third cell insulation layer may be between the substrate and the cell gate pattern, a first peripheral insulation layer, a second peripheral insulation layer, and a third peripheral insulation layer may be between the substrate and the peripheral gate pattern, and the second cell insulation layer and the third cell insulation layer include the same material as the respective second peripheral insulation layer and third peripheral insulation layer.