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