A semiconductor device includes a substrate, a stack structure, peripheral gate structures and residual spacers. The substrate includes a cell array region and a peripheral circuit region. The stack structure is disposed on the cell array region, having electrodes and insulating layers alternately stacked. The peripheral gate structures are disposed on the peripheral circuit region, being spaced apart from each other in one direction and having a peripheral gate pattern disposed on the substrate, and a peripheral gate spacer disposed on a sidewall of the peripheral gate pattern. The residual spacers are disposed on sidewalls of the peripheral gate structures, having a sacrificial pattern and an insulating pattern that are stacked. The insulating pattern includes substantially the same material as the insulating layers of the stack structure.