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