Semiconductor devices may include a stacked structure including interlayer insulating layers and gate electrodes alternately stacked in a vertical direction, a core region extending in the vertical direction in the stacked structure, a channel layer on a side surface of the core region and facing the gate electrodes and the interlayer insulating layers, a first dielectric layer, a data storage layer and a second dielectric layer, which are between the channel layer and the gate electrodes in order, and an anti-ferroelectric layer including a portion interposed between the first dielectric layer and a first gate electrode of the gate electrodes. The second dielectric layer may contact the channel layer. The anti-ferroelectric layer may be formed of an anti-ferroelectric material having a tetragonal phase.