Phase　change　memory　(PCM)　cells　based　on　Ge2Sb2Te5　were　synthesized　and　investigated.　Current-voltage　measurements　demonstrated　different　final　resistances.　Transmission　electron　microscopy　(TEM),　high　resolution　electron　microscopy　(HREM)　and　the　energy　dispersive　X-ray　spectroscopy　(EDS)　analyses　were　used　to　characterize　the　microstructures　of　the　PCM　cells.　The　architectures,　structures　and　defects　in　the　cells　including　the　deposited　elemental　distributions　and　the　interfacial　structures　between　electrodes　and　barrier　layers　were　studied　in　detail.