Provided is a nonvolatile memory device including a lower electrode on a substrate, an upper electrode on the lower electrode, a tunnel barrier pattern between the lower electrode and the upper electrode, and a fixed charge pattern in contact with the lower electrode and spaced apart from the tunnel barrier pattern with the lower electrode therebetween. The tunnel barrier pattern includes an anti-ferroelectric material. The lower electrode includes a first material. The upper electrode includes a second material. The first material and the second material have different work functions.