{HEAD ~ The spacer} preferably comprises {TAIL ~ a material} selected from the group comprising refractory metal silicides or their associated nitrides, such as, for example, titanium silicide, titanium nitride, and cobalt silicide 
{ HEAD ~ The spacer } preferably comprises { TAIL ~ a material } selected from the group comprising refractory metal silicides or their associated nitrides , such as , for example , titanium silicide , titanium nitride , and cobalt silicide
HEAD HEAD HEAD HEAD HEAD HEAD 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