Nonvolatile semiconductor memory device having tapered portion on side wall of charge accumulation layer

摘要

In a nonvolatile semiconductor memory device, a charge accumulation layer is formed between adjacent two device isolation regions, at least a portion of the charge accumulation layer sandwiched with the device isolation regions has side walls each having a taper angle of 80 degrees or more and less than 90 degrees so that the charge accumulation layer at a lower end has a width wider than that at an upper end, a size of an opening of each of the device isolation regions is 0.25 mum or less, and a gate length of a memory cell is 0.2 mum or less.