providing {TAIL ~ another ion implantation mask} which exposes {HEAD ~ a portion} of the source/base region; and 
providing { TAIL ~ another ion implantation mask } which exposes { HEAD ~ a portion } of the source / base region ; and
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH