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