Semiconductor memory devices, electronic systems including the same and fabricating methods of the same

Abstract

Semiconductor memory devices may include a cell substrate including a cell array region, first and second extension regions and a through region, a first mold structure including first gate electrodes stacked in a stepwise manner, a first interlayer insulating layer extending conformally on the first gate electrodes on the second extension region, a second interlayer insulating layer on the first interlayer insulating layer, a second mold structure including second gate electrodes on the second interlayer insulating layer and stacked on the first extension region in the stepwise manner, a channel structure in the first and second mold structures on the cell array region, a first cell contact structure in the first mold structure on the second extension region, and a second cell contact structure in the first and second mold structures on the first extension region. The first and second interlayer insulating layers may have different impurity concentrations.