Flash EEPROM preventing excessive erasure - injects electrons into floating gate of memory cells during erasure and extracts electrons during programming to force cells to enhancement level determined by set voltage

摘要

A source line is common to the memory cells, with each cell fitted with a control gate (1006) coupled to a word line. A drain (1002) is coupled to a corresp. bit line, while a source (1003) is linked to the source line. An electron injection gun simultaneously applies electrons to floating gates of several memory cells during erasing to force the memory cells into an enrichment mode with the cells defined by a first threshold voltage. An electron extraction acts on a selected floating gate for programming to force its cell into a second enrichment, under definition by a second threshold voltage. ADVANTAGE - Reliable and more rapid operation for both programming and erasing.