The spacer preferably comprises a material selected from {HEAD ~ the group} comprising {TAIL ~ refractory metal silicides} and nitrides 
comprising
The spacer preferably comprises a material selected from { HEAD ~ the group } comprising { TAIL ~ refractory metal silicides } and nitrides
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH