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