A novel Dual String NOR (DuSNOR) memory cell technology scalable to the 256 Mbit and 1 Mbit flash memories

We have developed a novel NOR-type flash memory technology named Dual String NOR (DuSNOR). In the DuSNOR cell array, two adjacent cell strings share a source line and up to 128 cell transistors can be attached to a string. This makes the cell size of DuSNOR smaller than NAND, without sacrificing the advantages of the NOR-type cell. Both the program and erase operations utilize the Fowler-Nordheim tunneling. DuSNOR cells with a cell size of 1.60 μm² was fabricated using 0.5 μm design rules. It was found that the DuSNOR cell has a fast operating speed, reduced overprogram and disturb problems, and excellent endurance characteristics. DuSNOR is a promising technology for high density, high speed, and random-access flash memories with a small cell size, excellent device characteristics and simplicity in the fabrication process