A phase-changeable memory device may include a substrate, an insulating layer on the substrate, first and second electrodes, and a pattern of a phase-changeable material between the first and second electrodes. More particularly, the insulating layer may have a hole therein, and the first electrode may be in the hole in the insulating layer. Moreover, portions of the second electrode may extend beyond an edge of the pattern of phase-changeable material. Related methods are also discussed.