Two Resistive Random Access Memory (RRAM) devices were designed with the thin Al2O3/thick HfO2 stack as a functional layer. These devices used different thickness of Al2O3 layer and same thickness of HfO2 layer. The fluctuation of the SET and the RESET voltages, the main obstacle which blocks the application of RRAMs based on transition metal oxide, leads to the instability of the RRAM. The random circuit breaker network.(RCB) model points out that the fluctuation of the voltages is the universal problem of RRAM devices and it originated from the working principles of devices. With this structure, the random formation and rupture of conducting filaments are limited within the Al2O3 film, which own lower k value, near the anode region instead of random formation and rupture in the whole functional layer. And experiments find that for the device with 5 nm Al2O3 film, the distributions of the 80% V-SET and V-RESET are limited within 0.2 V (from 0.6 V to 0.8 V) and 0.25 V (from -0.5 V to -0.25 V), respectively. For comparison, distributions for the device with 10 nm Al2O3 film are within 1.1 V (from 0.6 V to 1.7 V) and 1 V (from -13 V to 03 V), respectively. (C) 2014 Elsevier B.V. All rights reserved.