The generation mechanism of stress induced leakage current (SILC) in flash memory cell is studied by experiments. The result shows that the reliability problem under low electronic field stress is mainly caused by carriers charging and discharging inside the oxide, while under high electronic field, the trap-assisted tunneling and positive charge assisted tunneling induced charge variation of floating-gate is the major cause of flash memory cell failure. For both high and low electronic field stresses, the transient current and the steady-state current in SILC are calculated, respectively.