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