Double-layer stacked HfOx vertical RRAM is demonstrated for 3D cross-point architecture using a cost-effective fabrication process. Electrode/oxide interface engineering using TiON layer results in non-linear I-V suitable for the selector-less array. The fabricated HfOx vertical RRAM shows excellent performances such as reset current (<50μA), switching speed (∼50ns), switching endurance (>108 cycles), half-selected read disturbance immunity (>109 cycles), retention (>105s @125 oC). Moreover, a unique write/read scheme is proposed for 3D cross-point architecture. Analysis shows that for such 3D selector-less array, a large Ron (∼100k) from the non-linear I-V helps reduce the sneak path current, and a low interconnect resistance using metal planes as word lines reduces the undesirable voltage drop on the interconnect. As a conservative estimate, simulation shows that Mb-scale array without cell selector is achievable.