A memory device includes a cell stacked structure on a substrate, the cell stacked structure including insulation layers and gate patterns alternately stacked, a channel structure passing through the cell stacked structure, the channel structure extending in a vertical direction, a dummy structure on the substrate, the dummy structure being spaced apart from the cell stacked structure, and the dummy structure including insulation layers and metal patterns alternately stacked, a first through via contact passing through the dummy structure, the first through via contact extending in the vertical direction, and a first capping insulation pattern between a sidewall of the first through via contact and each of the metal patterns in the dummy structure, the first capping insulation pattern insulating the first through via contact from each of the metal patterns.