SEMICONDUCTOR DEVICES AND DATA STORAGE SYSTEMS INCLUDING THE SAME

A semiconductor device includes a peripheral circuit structure including a substrate, a circuit element on the substrate, connection patterns electrically connected to the circuit element, and a peripheral insulating structure on the circuit element, a memory cell structure on the peripheral circuit structure, the memory cell structure including interlayer insulating layers and gate electrodes alternately stacked on each other, an upper wiring, and a through-contact plug electrically connecting the upper wiring to an upper connection pattern in, which is in an uppermost position of the connection patterns relative to an upper surface of the substrate providing a base reference surface, wherein the peripheral circuit structure further includes a dam structure on the upper connection pattern, the peripheral insulating structure includes a first insulating layer on the circuit element and a side surface of the upper connection pattern and a second insulating layer, a capping layer, and a third insulating layer sequentially stacked on the first insulating layer, wherein the dam structure passes through the second insulating layer and contacts the upper connection pattern, and wherein the through-contact plug includes a lower portion passing through the dam structure and contacting the upper connection pattern and an upper portion on the lower portion.