Semiconductor devices and data storage systems including the same

Abstract

A semiconductor device includes a first semiconductor structure, and a second semiconductor structure on the first semiconductor structure. The second semiconductor structure includes a substrate having first and second regions, gate electrodes spaced apart from each other on the first region, extending by different lengths and including a pad region having an upper surface exposed upwardly, interlayer insulating layers alternately stacked with the gate electrodes, channel structures penetrating through the gate electrodes, gate contact plugs penetrating through the pad region of each of the gate electrodes and extending into the first semiconductor structure, and an insulating structure alternating with the interlayer insulating layers below each of the pad regions and surrounding the gate contact plugs. The insulating structure includes a first insulating layer and a second insulating layer surrounding at least a portion of the first insulating layer and including a material different from any of the first insulating layer.