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