In this study, the resistive switching performance of amorphous indium-gallium-zinc oxide (a-IGZO) resistive switching random-access memory (ReRAM) was improved by inserting a thin silicon oxide layer between silver (Ag) top electrode and a-IGZO resistive switching layer. Compared with the single a-IGZO layer structure, the SiO2/a-IGZO bi-layer structure exhibits the higher On/Off resistance ratio larger than 10(3), and the lower operation power using a smaller SET compliance current. In addition, good endurance and excellent retention characteristics were achieved. Furthermore, multilevel resistance states are obtained through adjusting SET compliance current and RESET stop voltage, which shows a promise for high-performance nonvolatile multilevel memory application. (C) 2015 Elsevier B.V. All rights reserved.