A method of forming a thin layer and a method of manufacturing a phase change memory device, the method of forming a thin layer including providing a first deposition source onto a substrate, the first deposition source not including tellurium; and providing a second deposition source onto the substrate, the second deposition source including a first tellurium precursor represented by the following Formula 1 and a second tellurium precursor represented by following the Formula 2: Te(CH(CH3)2)2  Formula 1 Ten(CH(CH3)2)2  Formula 2 wherein, in Formula 2, n is an integer greater than or equal to 2.