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Abstract

Contactless flash EPROM cell and array designs, and methods for fabricating the same result in a dense, segmentable flash EPROM chip. The flash EPROM cell is based on a drain-source-drain configuration, in which the single source diffusion is shared by two columns of transistors. The module includes a memory array having at least M rows and 2N columns of flash EPROM cells. M word lines, each coupled to the flash EPROM cells in one of the M rows of the flash EPROM cells, and N global bit lines are included. Data in and out circuitry is coupled to the N global bit lines which provide for reading and writing data in the memory array. Selector circuitry, coupled to the 2N columns of flash EPROM cells, and to the N global bit lines, provides for selective connection of two columns of the 2N columns to each of the N global bit lines so that access to the 2N columns of flash EPROM cells by the data in and out circuitry is provided across N global bit lines. The semiconductor substrate has a first conductivity type, a first well in the substrate of a second conductivity type, and a second well of the first conductivity type in the first well. The flash EPROM cells are made in the second well to allow application of a negative potential to at least one of the source and drain during an operation to charge the floating gate in the cells.

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First Claim