{HEAD ~ an insulative diffusion barrier layer} directly covering {TAIL ~ at least a portion} of the metal wiring, 
directly covering
{ HEAD ~ an insulative diffusion barrier layer } directly covering { TAIL ~ at least a portion } of the metal wiring ,
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH