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