Phase-change　materials　are　the　basis　for　next　generation　memory　devices,　but　the　fundamental　mechanism　of　the　phase　transitions　has　not　been　elucidated　clearly.　In　this　paper,　the　microstructure　treated　by　isothermal　and　the　laser　radiance　was　compared　by　Raman　spectroscopy.　It　was　found　that　the　peak　similar　to　105　cm(-1)　originated　from　GeTe4　tetrahedral　structure　and　the　intensity　of　this　peak　became　weak　with　the　enhancement　of　laser　pulse　energy　and　extension　of　annealing　time.　Moreover,　we　also　ascribed　the　Raman　peaks　in　specific　positions　to　the　GeTe4-nGen　(n=0,　1,　2,　3)　tetrahedral　structures.