Abstract: A bitwise bidirectionally rewritable nonvolatile semiconductor storage device capable of performing a high-speed data rewrite, while enhancing endurance characteristics and data-retention characteristics of a memory cell. To achieve high-speed generation of rewrite-bit information indicating that a data rewrite is needed or not, the structure employs a logic circuit corresponding to the number of change patterns of write conditions and concurrently compares between read-out data RO of memory at the start of the data rewrite and prepared write data DIN. After an electrical data rewrite of the memory, the data rewrite is verified based on the rewrite-bit information stored in an internal buffer circuit. This protects an already-rewritten memory cell from unnecessary additional rewrite.

Abstract: A memory array includes a resistive memory cell array having a first cell transistor and a resistance change element connected in series and a reference cell array having a second cell transistor and a resistance element connected in series. The second cell transistor of the reference cell array is connected to a reference source line, and the resistance element is connected to a reference bit line. A dummy memory cell is connected to the reference bit line in the memory cell array, and both ends of a resistance change element of the dummy memory cell are short-circuited through the reference bit line.

Abstract: A bitwise bidirectionally rewritable nonvolatile semiconductor storage device capable of performing a high-speed data rewrite, while enhancing endurance characteristics and data-retention characteristics of a memory cell. To achieve high-speed generation of rewrite-bit information indicating that a data rewrite is needed or not, the structure employs a logic circuit corresponding to the number of change patterns of write conditions and concurrently compares between read-out data RO of memory at the start of the data rewrite and prepared write data DIN. After an electrical data rewrite of the memory, the data rewrite is verified based on the rewrite-bit information stored in an internal buffer circuit. This protects an already-rewritten memory cell from unnecessary additional rewrite.

Abstract: A memory array includes a resistive memory cell array having a first cell transistor and a resistance change element connected in series and a reference cell array having a second cell transistor and a resistance element connected in series. The second cell transistor of the reference cell array is connected to a reference source line, and the resistance element is connected to a reference bit line. A dummy memory cell is connected to the reference bit line in the memory cell array, and both ends of a resistance change element of the dummy memory cell are short-circuited through the reference bit line.