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