Patent attributes
Each nonvolatile memory cell transistor has such directivities that a current flows only from the drain to the source and that charge is exchangeable only at the source. The source of one of a pair of memory cell transistors connected to each word line is connected to the drain of the other memory cell transistor, and the drain of the one memory cell transistor is connected to the source of the other. During a data rewrite operation, reverse voltages are applied to the sources and drains of the pair of memory cell transistors. Because of the directivities of each memory cell transistor, charge is exchanged with a charge accumulation layer only in the source region. This makes the data rewritable in only one of the pair of memory cell transistors. As a result, data is rewritable on a memory cell basis without increasing the memory cell size.
