Abstract: An embodiment, relates to a phase changeable memory cell. The phase changeable memory cell is formed with an ultra small contact area formed by filament conductive path. This contact area between a heating electrode and phase changeable material layer is determined by the forming of filament path, which is conductive and much smaller in cross-sectional area than the minimum area that can be achieved by lithography. This leads to high heating efficiency and ultra-low programming current. As the disclosed structure has no requirement on endurance for the formed filament and use phase changeable material rather than filament-forming material to provide high on/off resistance ratio, drawbacks of filament-forming material on low endurance and low sensing margin are avoided in the proposed cell structure.