Resistive random-access memory (RRAM) structures are formed with ultra-thin RRAM-functional layers, thereby improving memory margins. Embodiments include forming an interlayer dielectric (ILD) over a bottom electrode, forming a sacrificial layer over the ILD, removing a portion of the ILD and a portion of the sacrificial layer vertically contiguous with the portion of the ILD, forming a cell area, forming a metal layer within the cell area, forming an interlayer dielectric structure above or surrounded by and protruding above the metal layer, a top surface of the interlayer dielectric structure being coplanar with a top surface of the sacrificial layer, removing the sacrificial layer, forming a memory layer on the ILD and/or on side surfaces of the interlayer dielectric structure, and forming a dielectric layer surrounding at least a portion of the interlayer dielectric structure.