RETROGRADE CHANNEL DOPING TO IMPROVE SHORT CHANNEL EFFECT

摘要

A memory semiconductor cell (30) comprises a gate region (16), a source region (14) and a drain region (14). A channel region (17) is formed between the source region (14) and the drain region (14). The channel region (17) comprises a first channel portion (33) with a first concentration of doping material, the first channel portion (33) disposed adjacent to an edge of the channel region (17) closest to and substantially parallel to the gate region (16). The channel region (17) further comprises a second channel portion (31) with a second concentration of doping material, the second channel portion (31) disposed substantially parallel to the first channel portion (33) and a third channel portion (32), disposed between the first channel portion (33) and the second channel portion (31), with a third concentration of doping material. The third concentration is lower than the first concentration and lower than the second concentration. The memory cell may be one of two general types of non-volatile memory, a floating gate cell or a nitride read only memory (NROM), whereby layer (12B) in a floating gate or a nitride layer respectively.