Semiconductor device with stacked structure

Abstract

A semiconductor device includes a lower structure, a stack structure on the lower structure and extending from a memory cell region into a connection region, gate contact plugs on the stack structure in the connection region, and a memory vertical structure through the stack structure in the memory cell region, wherein the stack structure includes interlayer insulating layers and horizontal layers alternately stacked, wherein, in the connection region, the stack structure includes a staircase region and a flat region, wherein the staircase region includes lowered pads, wherein the flat region includes a flat pad region, a flat edge region, and a flat dummy region between the flat pad region and the flat edge region, and wherein the gate contact plugs include first gate contact plugs on the pads, flat contact plugs on the flat pad region, and a flat edge contact plug on the flat edge region.