Driving method of nonvolatile memory and nonvolatile memory used in the same method

Abstract

To increase a cell current ratio of a program state to an erase state of two bit storage nonvolatile memory cells and reduce power consumption, a program state of MONOS-typed memory cells is a state where electrons are injected into two local regions near drain and source junction edges, an erase state is a state where the electrons injected into the two local regions are neutralized or holes are injected, and a read bias is a linear region. A cell current in the program state can be suppressed since charges injected into the source side suppress introduction of electron carriers required for formation of a conductive channel and charges injected into the drain side limit the formation of the conductive channel near the drain side. Accordingly, a read current can be reduced, a cell current ratio can be enhanced, and moreover, a margin of a reading operation can be increased.