NONVOLATILE SEMICONDUCTOR STORAGE DEVICE

摘要

PURPOSE:To emancipate a user from troubles of time control and to make the device easy to handle by realizing the proper time for writing or erasing in each memory cell without compelling the user to perform troublesome time control. CONSTITUTION:A pulse generating circuit 32 is started by a controlling signal i.e. a program signal Po given from the outside for writing or erasing, and generates a pulse signal Pi of specified time width. An MOS transistor of floating gate structure is used in each memory cell that constitutes a memory matrix 10. In the case of floating gate structure, writing of storage data is made by accumulation of charge in the gate. Erasing is made by discharging accumulated charges of the gate. Accumulation of charges of the gate or discharging of charges from the gate is made in a gate writing circuit 24 or an erasing circuit 26 by using the high voltage generated in a writing/erasing voltage generating circuit 28.