A structure including a bottom electrode, a phase change material layer, the phase change material layer includes a similar lattice constant as a lattice constant of the substrate, a top electrode on and vertically aligned with the phase change material layer, a dielectric material horizontally isolating the bottom electrode from the top electrode and the phase change material layer. A structure including a phase change material layer selected from amorphous silicon, amorphous germanium and amorphous silicon germanium, a top electrode on the phase change material layer, a bottom electrode, a dielectric material isolating the bottom electrode from the top electrode and the phase change material layer. Forming a bottom electrode, forming a phase change material layer adjacent to the bottom electrode, forming a top electrode above the phase change material, forming a dielectric material horizontally isolating the bottom electrode from the top electrode and the phase change material layer.