Samsung patent application US20110205410 proposes to etch holes in dielectric above each photodiode and place color filters inside the holes to reduce optical stack height. "The interlayer insulating layers defines an opening located on an upper portion of the photoelectric conversion device. A color filter is disposed in the opening, and a planarization layer fills the opening on the color filter. The planarization layer has a refractive index which is greater than an average refractive index of the interlayer insulating layers:"
This sounds to me quite similar to what ST is doing in its image sensors, as revealed by Chipworks:
Samsung application claims priority from Feb. 19, 2010. Given Chipworks found ST sensor in the product on the market already, I'd guess ST work has started well before Samsung's filing date.