NONVOLATILE SEMICONDUCTOR MEMORY DEVICE

摘要

PURPOSE:To reduce current consumption and to prevent a voltage drop during a write operation by a method wherein a memory cell between a selective cell and a bit line is turned on and a selective write operation is executed by using a tunnel of an electric charge between a semiconductor region of a first conductivity type and a floating gate. CONSTITUTION:A NAND cell is constituted in such a way that two or more cells having a floating gate 4 and a control gate 6 are connected in series so as to use a source-drain diffusion layer 9 in common; a memory array is constituted by arranging the NAND cell in a matrix form. The memory cells execute a write operation by tunneling an electron between the floating gate 4 and a substrate 1 where a well 1' has been formed. That is to say, an electron of collected bits is extracted collectively from the floating gate 4 to the well 1' and the bits are erased; then, the electron is injected selectively from a bit line to the floating gate 4. Because the write operation is executed not by injecting a hot electron but by using a tunnel, current consumption is reduced; a voltage drop can be prevented.