CEA-Leti

CEA Leti has a track record of driving visionary research.
The latest such program is well known as the COOL-CUBE, a monolithic integration of two (in future even more) layers of circuitry vertically stacked. As wafer-fab experts can tell you, running a wafer again multiple times through fab, after you finished processing all the diffusion and metal layers needed manufacture a wafer with typical SoC circuitry, is very challenging. It takes special recipes and very careful processing to NOT ruin transistor performance on the first layer, while adding the second layer on top of it.