A phase-changeable memory device includes a substrate having a contact
region on an upper surface thereof. An insulating interlayer on the
substrate has an opening therein, and a lower electrode is formed in the
opening. The lower electrode has a nitrided surface portion and is in
electrical contact with the contact region of the substrate. A
phase-changeable material layer pattern is on the lower electrode, and an
upper electrode is on the phase-changeable material layer pattern. The
insulating interlayer may have a nitrided surface portion and the
phase-changeable material layer may be at least partially on the nitrided
surface portion of the insulating interlayer. Methods of forming
phase-changeable memory devices are also disclosed.