{HEAD ~ A second asymmetric etching process} is performed to remove {TAIL ~ a portion} of the first oxide layer by using the remaining nitride layer as a mask until about 50% to 90% portion of the first oxide layer is removed 
is performed to remove
{ HEAD ~ A second asymmetric etching process } is performed to remove { TAIL ~ a portion } of the first oxide layer by using the remaining nitride layer as a mask until about 50 % to 90 % portion of the first oxide layer is removed
HEAD 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH