A series of complex HfO2/Al2O3 layer by layer resistive random access memory(RRAM) structure grown by atomic layer deposition are investigated. The modulation of forming voltage can be achieved by controlling the number of Al2O3 layers in HfO 2 devices. In addition, the crystallization temperature of HfO 2 based RRAM devices can also be improved by insetting Al 2O3 layers in HfO2 film. Compared with pure HfO2 device, a significant improvement in resistive switching properties such as forming voltage variation and the distribution of HRS/LRS during resistance switching is demonstrated in the HfO2/Al 2O3 layer by layer devices. Moreover, good endurance characteristic and highly reliable multibit operation are also achieved in this device structure.