High-density data storage (HDDS) is urgently required to address ongoing rapid increases in amounts of information. Here we present a prototype sandwich device that has ternary data-storage performance. Three characteristic currents can be read out using a certain constant voltage after removal of the applied voltage. Two electron pull groups and one electron push group are identified as the species responsible for electron flow. We believe that our observation will offer an interesting and useful theoretical approach for a huge increase in the memory density of potential future devices.