SEMICONDUCTOR DEVICES AND DATA STORAGE SYSTEMS INCLUDING THE SAME

A semiconductor device includes a first substrate structure including a substrate, circuit elements, and first bonding metal layers, and a second substrate structure connected to the first substrate structure. The second substrate structure includes a plate layer, gate electrodes stacked in a first direction below the plate layer, separation regions penetrating through the gate electrodes and extending in a second direction and spaced apart from each other in the second direction, an insulating region extending from an upper surface of the plate layer and penetrating through the plate layer and at least one of the gate electrodes between the separation regions, and second bonding metal layers connected to the first bonding metal layers. The insulating region has inclined side surfaces such that a width of the insulating region decreases in a direction toward the first substrate structure.