a phase - changeable memory device comprises a substrate and an access transistor formed in and / or on the substrate . laterally spaced apart first and second conductive patterns are disposed on the substrate and have opposing sidewalls . a conductor electrically connects the first conductive region to a source / drain region of the access transistor . a phase - changeable material region is disposed between the first and second conductive patterns and contacts the opposing sidewalls of the first and second conductive patterns . contact areas between the conductive patterns and the phase - changeable material region are preferably substantially smaller than contact areas at which the conductive patterns contact conductors connected thereto , such that high current densities may be developed in the phase - changeable material . methods of fabricating such devices are also discussed .