In this work, a comprehensive study of Ge-rich Phase Change Memory set and reset state retention realized by coupling electrical and physical characterizations is presented. The presence of amorphous residuals inside the active region of PCM devices is, for the first time, demonstrated through High Resolution Scanning Transmission Electron Microscopy. The role of such formations was studied by means of electrical character-ization and supported by modeling analysis. By comparing the low and high state resistive behavior the retention physics has been analytically modeled with the same framework for both states.