a third semiconductor layer formed on the second semiconductor layer in {HEAD ~ exactly the same size} and {TAIL ~ pattern} as the latter 
a third semiconductor layer formed on the second semiconductor layer in { HEAD ~ exactly the same size } and { TAIL ~ pattern } as the latter
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH