Semiconductor device and data storage system including same

The invention relates to a semiconductor device and a data storage system including the same. The semiconductor device includes: a first substrate; the second substrate comprises a first area and a second area; a stack structure in the first region and extending from the first region to the second region, the stack structure including an interlayer insulating layer and a gate layer, in which the gate layer includes a gate pad having a step shape in the second region; a cover insulating layer at least partially covering the stacked structure; an upper insulating layer on the stacked structure and the cover insulating layer; a peripheral contact structure including a plurality of through vias contacting the second substrate and spaced apart from the gate layer, and a peripheral contact pattern on the plurality of through vias and connecting at least a portion of the plurality of through vias to each other; a memory vertical structure; a support vertical structure; and a gate contact plug on the gate pad to be e