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