Provided are nonvolatile memory transistors and devices including the nonvolatile memory transistors. A nonvolatile memory transistor may include a channel element, a gate electrode corresponding to the channel element, a gate insulation layer between the channel element and the gate electrode, an ionic species moving layer between the gate insulation layer and the gate electrode, and a source and a drain separated from each other with respect to the channel element. A motion of an ionic species at the ionic species moving layer occurs according to a voltage applied to the gate electrode. A threshold voltage changes according to the motion of the ionic species. The nonvolatile memory transistor has a multi-level characteristic.