Fairchild Imaging presented a 4T pixel paper on SPIE Astronomical Telescopes and Instrumentation Conference, 23-28 June 2008, Marseille, France. It shows quite a conventional 6.5um pixel made in 0.18um process. What really sets it apart is a very low full well - only 1.5Ke at most.
Update: As mentioned in comments, probably the full well is limited by column amplifier in high-gain mode. The pixel's native full well is probably higher, albeit the paper does not give an explicit number.
Update #2: Two sentences removed, as said in comments.