{TAIL ~ The drain region}, the source/base region, and {HEAD ~ the cathode region} have a second conductivity type 
{ TAIL ~ The drain region } , the source / base region , and { HEAD ~ the cathode region } have a second conductivity type
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH