RRAM device consists M-I-M (Metal - Insulator - Metal) structure and in most of the RRAM device insulating layer plays important role in resistive switching between HRS (High Resistance state) and LRS (Low Resistance State).
Dash, C. S., and S. R. S. Prabaharan. "Science and Technological Understanding of Nano-ionic Resistive Memories (RRAM)." Nanoscience & Nanotechnology-Asia 9, no. 4 (2019): 444-461.