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