Embodiments of the invention provide a semiconductor memory device. In some embodiments, the device includes a bottom electrode extending in a y-direction relative to top surface of a substrate and a top electrode extending in an x-direction relative to the top surface of the substrate. An active area is located at the cross-section between the bottom electrode and the top electrode and is located on vertical side walls extending in a z-direction of the semiconductor memory device with respect to the top surface of the substrate. An insulating layer is located in the active area in between the top electrode and the bottom electrode.