{HEAD ~ each} of {TAIL ~ said pair} of SiGe mixed crystal regions including a main part formed right underneath an uppermost part of said SiGe mixed crystal region, said main part having a sidewall surface, 
of
{ HEAD ~ each } of { TAIL ~ said pair } of SiGe mixed crystal regions including a main part formed right underneath an uppermost part of said SiGe mixed crystal region , said main part having a sidewall surface ,
HEAD HEAD HEAD HEAD HEAD REL 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 OTH OTH