{TAIL ~ An impurity layer} with an impurity concentration different from that of the first semiconductor substrate is formed on or in {HEAD ~ the surface area} exposed to the etched portion of the first and second semiconductor substrates 
{ TAIL ~ An impurity layer } with an impurity concentration different from that of the first semiconductor substrate is formed on or in { HEAD ~ the surface area } exposed to the etched portion of the first and second semiconductor substrates
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH