{HEAD ~ A second polishing step} is performed to remove {TAIL ~ a portion} of the remaining portion of the silicon oxide layer until the silicon nitride layer is exposed 
is performed to remove
{ HEAD ~ A second polishing step } is performed to remove { TAIL ~ a portion } of the remaining portion of the silicon oxide layer until the silicon nitride layer is exposed
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH