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