In this work, tantalum oxide (TaOJ based ring contact Resistive Random Access Memory (RRAM) devices with varying TaOx thicknesses (5, 10 and 15 nm) were demonstrated and evaluated. TaOx layers were deposited using atomic layer deposition and were in contact with a Platinum (Pt) top electrode and Tantalum (Ta) sidewall electrode. RRAM devices with different TaOx thickness were compared to investigate the scaling capabilities for potential 3D RRAM application. It was found that as the TaOx thickness scaled to 5 nm, reasonable switching characteristics with less cycling variations were obtained which indicates that a thickness of 5 nm TaOx is capable of being implemented in sidewall RRAM geometries.