The method 13, wherein {HEAD ~ a number} of masking steps used for forming the crossbar array is independent of {TAIL ~ a number} of metal and insulator layers of the crossbar array 
The method 13 , wherein { HEAD ~ a number } of masking steps used for forming the crossbar array is independent of { TAIL ~ a number } of metal and insulator layers of the crossbar array
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH