NONVOLATILE SEMICONDUCTOR MEMORY AND ITS OPERATING METHOD

摘要

PURPOSE:To reduce the variation of the threshold value of a cell after drawing electric charge by injecting avalanche hot carrier(AHC) into a charge storage part after emitting electrons. CONSTITUTION:When an erasing operation controller 30 is activated, F-N tunnel erase control circuit 26 is supplied with a signal S2 to be activated. Then, a memory cell array 14 is supplied with an erase signal S3 so that electron is drawn from a floating gate by F-N tunnel current. Subsequently, AHC injection control circuit 28 is supplied with a signal S4 to supply the memory cell array 14 with an injection signal S5. Accordingly, AHE or AHH is injected into the floating gate so that the threshold value of a cell is tuned. Consequently, the cell threshold value having caused variation after drawing of electron by the F-N tunnel current converges on a balanced threshold voltage.