Metal oxides are the most widely used material for the resistive switching layer of memristors. Nevertheless, the majority of oxide-based memristors exhibit binary switching, restricting the emulation of neuronal synaptic behaviors. In this paper, the shift from digital-to-analog switching behavior is achieved by inserting an Al₂O₃ layer atop Zr-doped HfO₂. The TiN/Al₂O₃/HZO/W/Si device exhibits long resistance state retention time and consistency. In addition, by applying a varying voltage, the device exhibits up to 20 continuous resistance states, which is highly significant for high-density storage. Upon the application of a programmable pulse signal, the device’s conductance undergoes continual alteration, reflecting long-term potentiation (LTP) and long-term depression (LTD) synaptic characteristics. The conduction mechanism of the device is studied through physical model fitting and schematic diagrams.