FOUR-CONDITION MEMORY CELL

摘要

PROBLEM TO BE SOLVED: To provide a small four-level memory cell in which a condition is easily discriminated and electrical programming is enabled. SOLUTION: This memory cell has an insulated control gate 24, on a first conductivity type channel region, and second conductivity type source and drain regions, and each of the source and drain regions has near the channel an area of low dope level, and a floating gate, 28 and 29, covering at least a part of each area of low dope level. The thickness of an insulating body 25 under the floating gates 28 and 29 is thinner than that of the insulating body under the control gate 24. It is so thin that injection of load is enabled by tunnel effect.