In this paper, we demonstrated different filament formation abilities of two metal oxide layers for reliable switching uniformity of resistive random access memory (ReRAM). We observed, for the first time, set operation exhibited stepwise operation in Pt top electrode (TE)/Ti/HfOx/TaOx/Pt bottom electrode (BE) due to different filament formation abilities of HfOx and TaOx. Compared with the Pt/Ti/HfOx/Pt, the inserted TaOx in the triple-layer can act as a filament control layer for uniform switching. Thus, additionally inserted TaOx plays an important role in ReRAM for its reliable switching. To achieve lower operating current and more uniform switching in the Pt/Ti/HfOx/TaOx/Pt structure, we had controlled oxygen distributions of TaOx, layer. Consequently, we achieved a very low operating current (similar to 45 mu A) without switching uniformity degradation. (C) 2014 Elsevier Ltd. All rights reserved.