forming {TAIL ~ a second interconnect structure} having {HEAD ~ a second interfacial structure} different from the first interfacial structure, 
forming { TAIL ~ a second interconnect structure } having { HEAD ~ a second interfacial structure } different from the first interfacial structure ,
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH