A nonvolatile memory device includes a gate structure including inter-gate insulating patterns that are vertically stacked on a substrate and gate electrodes interposed between the inter-gate insulating patterns, a vertical active pillar connected to the substrate through the gate structure, a charge-storing layer between the vertical active pillar and the gate electrode, a tunnel insulating layer between the charge-storing layer and the vertical active pillar, and a blocking insulating layer between the charge-storing layer and the gate electrode. The charge-storing layer include first and second charge-storing layers that are adjacent to the blocking insulating layer and the tunnel insulating layer, respectively. The first charge-storing layer includes a silicon nitride layer, and the second charge-storing layer includes a silicon oxynitride layer.