Sony patent application US20150029374 "Image sensor, manufacturing apparatus and method, and imaging apparatus" by Yoshiaki Kitano proposes a back-illuminated sensor where at least some of SF, SEL and RST and even TG transistors are placed in a layer grown on top of the photodiode - possibly a local epi, although Sony does not use this word. The transistors are FinFET-like, sort of. Since FinFETs have almost no bulk, the SF gain should be much closer to unity and its effective gate cap should be minimal. The PD area can be expanded to almost whole pixel area:
Update: While we are at Sony news many times this week, WSJ quotes Masahiro Ono, an analyst at Morgan Stanley MUFG Securities, saying "Sony’s image sensors are the best in the world and are at least four years ahead of their competitors." If Sony manages to release this FinFET pixel into production, I would agree with that 4 years ahead claim.