Quad+bit storage in trap based flash design using single program and erase entity as logical cell

Abstract

Flash memory systems and methodologies are provided herein for facilitating single logical cell erasure and quad or more bit storage in a flash device. The single logical cell erasure can be accomplished by employing a single program and erase entity as a single logical cell. The single program and erase entity is a combination of neighboring drain/source regions of two adjacent physical memory cells. By mapping two adjacent physical cells as a single logical cell, the flash memory device can be programmed and erased on a single bit or variable bit length basis. The memory cells can contain four or more data states, and each of the two adjacent memory cells in the single program and erase entity can be programmed independently from each other. As a result, the single program and erase entity can store four or more bits.

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