1. Field of the Invention
The present invention relates to a nonvolatile semiconductor memory device and method of manufacturing the same.
2. Description of the Related Art
Electrically erasable programmable nonvolatile memories include a flash memory as well known in the art, which comprises a memory cell array of NAND-connected or NOR-connected memory cells having a floating gate structure. A ferroelectric memory is also known as a nonvolatile fast random access memory.
On the other hand, technologies of pattering memory cells much finer include a resistance variable memory, which uses a variable resistor in a memory cell as proposed. Known examples of the variable resistor include a phase change memory element that varies the resistance in accordance with the variation in crystal/amorphous states of a chalcogenide compound; an MRAM element that uses a variation in resistance due to the tunnel magneto-resistance effect; a polymer ferroelectric RAM (PFRAM) memory element including resistors formed of a conductive polymer; and a ReRAM element that causes a variation in resistance on electrical pulse application (Patent Document 1: JP 2006-344349A, paragraph 0021).
The resistance variable memory may configure a memory cell with a serial circuit of a Schottky diode and a resistance variable element in place of the transistor. Accordingly, it can be stacked easier and three-dimensionally structured to achieve much higher integration advantageously (Patent Document 2: JP 2005-522045A).