The memory circuit 6, wherein {HEAD ~ the third impurity concentration} is identical to the first impurity concentration, and {TAIL ~ the fourth impurity concentration} is identical to the second impurity concentration 
The memory circuit 6 , wherein { HEAD ~ the third impurity concentration } is identical to the first impurity concentration , and { TAIL ~ the fourth impurity concentration } is identical to the second impurity concentration
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH