{TAIL ~ Erasure} is performed in one operation in the erase block , and a rewrite operation is performed on a bit or {HEAD ~ bits} whose threshold voltage Vt is lower than an erase operation lower limit value  
{ TAIL ~ Erasure } is performed in one operation in the erase block , and a rewrite operation is performed on a bit or { HEAD ~ bits } whose threshold voltage Vt is lower than an erase operation lower limit value
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH