We have been investigated phase-change with temperature and electric field in chalcogenide Ge$_2$Sb$_2$Te$sub$5/ thin film. T$sub$c/(crystallization temperature) is confirmed by measuring the resistance with the varying temperature on the hotplate. We have measured I-V characteristics with Ge$_2$Sb$_2$Te$sub$5/ chalcogenide thin film. It is compared with I-V characteristics after impress the variable pulse. The pulse has variable height and duration.