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