The semiconductor filled portion of {TAIL ~ each trench} then serves as a drain and {HEAD ~ source} of a field effect transistor 
The semiconductor filled portion of { TAIL ~ each trench } then serves as a drain and { HEAD ~ source } of a field effect transistor
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH