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