Non-volatile semiconductor memory including memory cells having different charge exchange capability

Abstract

According to the present invention, the above-described objects can be achieved by a semiconductor storage device including: memory cells for storing data by accumulating or not accumulating charges, such as electrons, into floating gate; wherein the memory cell includes first memory cells having first charge exchange capability with respect to a charge exchange for the floating gate, and second memory cells having second charge exchange capability, so that data to be returned can be stored. In the semiconductor storage device according to the present invention, when all erase or all write (program) is performed to the memory cells, the first memory cells become to have a different threshold voltage from the second memory cells according to the different charge exchange capability of the memory cells, thus data to be returned can be read out. In a semiconductor storage device according to the present invention including memory cells for storing data by accumulating or not accumulating electrons on a floating gate FG, data to be returned can be stored by using the memory cells as first memory cells Q,having a first charge exchange capability and second memory cells Q,having a second charge exchange capability. The memory cell scan maintain a different threshold voltage according to different charge exchange capabilities of the memory cell, and therefore, it becomes possible to read out the initial data to be returned by all erasing to the memory cells.