{HEAD ~ A first polishing step} is performed to remove {TAIL ~ a portion} of the silicon oxide layer until a thickness of the remaining portion of the oxide layer reaches a predetermined thickness 
{ HEAD ~ A first polishing step } is performed to remove { TAIL ~ a portion } of the silicon oxide layer until a thickness of the remaining portion of the oxide layer reaches a predetermined thickness
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 OTH OTH OTH OTH