Ring heater for a phase change memory device

摘要

A ring shaped heater (26) surrounds a chalcogenide region (36) along the length of a cylindrical solid phase portion (35) thereof defining a change phase memory element. The chalcogenide region (36) is formed in a sub-lithographic pore (34), so that a relatively compact structure is achieved. Furthermore, the ring contact between the heater and the cylindrical solid phase portion (35) results in a more gradual transition of resistance versus programming current, enabling multilevel memories to be formed.