The control gate electrode 315 may be {HEAD ~ a polysilicon film} doped with {TAIL ~ impurities} 
The control gate electrode 315 may be { HEAD ~ a polysilicon film } doped with { TAIL ~ impurities }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL