That's not a minor development:
"Sony’s new architecture is an advancement in stacked CMOS image sensor technology. Using its proprietary stacking technology, Sony packaged the photodiodes and pixel transistors on separate substrates stacked one atop the other.
In conventional stacked CMOS image sensors, by contrast, the photodiodes and pixel transistors sit alongside each other on the same substrate. The new stacking technology enables adoption of architectures that allow the photodiode and pixel transistor layers to each be optimized, thereby approximately doubling saturation signal level relative to conventional image sensors and, in turn, widening dynamic range."