In a method of manufacturing a phase-change memory unit, a lower electrode electrically connected to a contact region is formed on a substrate. A preliminary phase-change material layer is formed on the lower electrode using a chalcogenide compound doped with carbon, or carbon and nitrogen. A phase-change material layer is obtained by doping a stabilizing metal into the preliminary phase-change material layer. An upper electrode is formed on the phase-change material layer. Since the phase-change material layer may have improved electrical characteristics, stability of phase transition and thermal stability, the phase-change memory unit may have reduced set resistance, enhanced durability, improved reliability, increased sensing margin, reduced driving current, etc.