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