This etch is continued until {HEAD ~ the silicon nitride} is removed from {TAIL ~ both contact regions} 
is removed from
This etch is continued until { HEAD ~ the silicon nitride } is removed from { TAIL ~ both contact regions }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL