METHOD AND APPARATUS FOR APPLYING PROGRAM VOLTAGE TO NONVOLATILE SEMICONDUCTOR MEMORY

摘要

PURPOSE:To extend the service life of a memory and to improve the reliability by applying a program voltage pulse in the case of electron injection and extraction to/from a floating gate while being divided into the plural number of times and applying injection and extraction little by little. CONSTITUTION:A chopper circuit 3 receiving a rectangular wave having a program voltage Vpp by a boosting circuit 1 outputs plural pulse signals with a prescribed width by a control signal from a control circuit 5. A limiter 7 having parallel connection of plural limiters having different limits is driven sequentially from a lower limit value with a selection signal from the circuit 5 and the limiter with a limit equal to the highest voltage Vpp is driven finally. The output of the limiter 7 is plural pulse trains whose peak rises stepwise and they are applied to a memory. Thus, the insulation breakdown of a tunnel oxide film is reduced to extend the service life of the memory and the program voltage application method and apparatus whose reliability is improved is obtained.