As Flash memories are approaching their ultimate scaling limit, reversible resistance switching attracts considerable interest because of its potential for high density non volatile memory devices. Resistive switching phenomena have been reported in many transition metal oxide films such as TiO 2 or MO. This work investigates the feasibility of emerging resistive- switching devices with NiO active dielectric layer on top of a pillar W bottom electrode. Reversible and repetitive switching is demonstrated for ReRAM cells with diameters ranging from 0.18 to 1 mum. Scaling and cycling capabilities are discussed and preliminary TEM results enable apprehending reliability issues and failure mechanisms.