A polycrystalline silicon film is formed on a surface of {HEAD ~ a trench} and on a surface of {TAIL ~ a silicon nitride film} 
A polycrystalline silicon film is formed on a surface of { HEAD ~ a trench } and on a surface of { TAIL ~ a silicon nitride film }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL