| 摘要 |
An ultra high density flash EEPROM provides increased nonvolatile storage capacity. A memory array includes densely packed memory cells, each cell having a pillar of semiconductor material that extends outwardly from a working surface of a substrate. The pillar includes source/drain and body regions and has a number of sides. A pair of vertically stacked floating gates is included on at least one of two sides of the pillar. A control gate line also passes through each memory cell. Each memory cell is associated with a control gate line so as to allow selective storage and retrieval of data on the floating gates of the cell. Both bulk semiconductor and silicon-on-insulator embodiments are provided. If a floating gate transistor is used to store a single bit of data, an area of only F2 is needed per bit of data, where F is the minimum lithographic feature size. If multiple charge states (more than two) are used, an area of less than F2 is needed per bit of data.
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