The present disclosure relates to a method of manufacturing a memory device. The method is performed by forming an inter-layer dielectric (ILD) layer over a substrate, and forming an opening within a dielectric protection layer over the ILD layer. A bottom electrode layer is formed within the opening and over the dielectric protection layer. A chemical mechanical planarization (CMP) process is performed on the bottom electrode layer to form a bottom electrode structure having a planar upper surface and a projection that protrudes outward from a lower surface of the bottom electrode structure to within the opening. A memory element is formed over the bottom electrode structure, and a top electrode is formed over the memory element.