| 摘要 |
<p>PURPOSE:To obtain the erasable nonvolatile memory while keeping the area of a memory cell almost the same as that of an EPROM by automatically stopping erasing in the memory device and controlling a threshold value into a value appropriate or reading out in the semiconductor nonvolatile memory device in which electrical erasing is possible with the memory cell as small as the EPROM. CONSTITUTION:When a pulse signal EE to indicate the starting of an erasing mode is inputted to an FF 28 and the erasing mode is obtained, an EM becomes a high level, grounds all the word lines 30 through a row decoder 29, turns on column selecting gates 25 and 26 through column decoders 31 and 32, and turns on an erasing mode selecting gate 27 by the EM. Thus, resetting MOSFETs 35 and 36 for discharging electric charge stored in a data line 33 are turned on for fixed time determined by a delay circuit 37, next, an FF 39 is set by a pulse generated using a delay circuit 38, and the sources of a memory part and a dummy memory part are connected through switches 8 and 9 to erasing high voltage VPP.</p> |
