A portion of the control gate could extend into a trench formed into the substrate, wherein the drain region is formed underneath the trench, and {HEAD ~ the channel region} has {TAIL ~ a first portion} extending along the trench sidewall and a second portion extending along the substrate surface 
A portion of the control gate could extend into a trench formed into the substrate , wherein the drain region is formed underneath the trench , and { HEAD ~ the channel region } has { TAIL ~ a first portion } extending along the trench sidewall and a second portion extending along the substrate surface
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH