Embodiments of a semiconductor memory device include a substrate having a first region with peripheral devices, a second region with one or more memory arrays, and a third region between the first and the second regions. The semiconductor memory device also includes a protective structure for peripheral devices. The protective structure for peripheral devices of the semiconductor memory device includes a first dielectric layer and a barrier layer disposed on the first dielectric layer. The protective structure for peripheral devices of the semiconductor memory device further includes a dielectric spacer formed on a sidewall of the barrier layer and a sidewall of the first dielectric layer, wherein the protective structure is disposed over the first region and at least a portion of the third region.

A three-dimensional semiconductor device is provided including main separation structures disposed on a substrate, and extending in a first direction, parallel to a surface of the substrate; gate electrodes disposed between the main separation structures; a first secondary separation structure penetrating through the gate electrodes, between the main separation structures, and including a first linear portion and a second linear portion, having end portions opposing each other; and second secondary separation structures disposed between the first secondary separation structure and the main separation structures, and penetrating through the gate electrodes. The second secondary separation structures have end portions opposing each other between the second linear portion and the main separation structures.

Embodiments of a semiconductor memory device include a substrate having a first region with peripheral devices, a second region with one or more memory arrays, and a third region between the first and the second regions. The semiconductor memory device also includes a protective structure for peripheral devices. The protective structure for peripheral devices of the semiconductor memory device includes a first dielectric layer and a barrier layer disposed on the first dielectric layer. The protective structure for peripheral devices of the semiconductor memory device further includes a dielectric spacer formed on a sidewall of the barrier layer and a sidewall of the first dielectric layer, wherein the protective structure is disposed over the first region and at least a portion of the third region.