A resistive random-access memory (RRAM) device includes a bottom electrode, a high work function layer, a resistive material layer, a top electrode and high work function spacers. The bottom electrode, the high work function layer, the resistive material layer and the top electrode are sequentially stacked on a substrate, wherein the resistive material layer includes a bottom part and a top part. The high work function spacers cover sidewalls of the bottom part, thereby constituting a RRAM cell. The present invention also provides a method of forming a RRAM device.