I am wondering why don't we make processors such as CPUs with 1000s of stacked layers to make use of space in the third dimension now that we have three-dimensional transistors. To be clear I'm referencing making something of a rectangular-prism shaped processor.
To be clear there's a vast amount I am not aware of when it comes to processor manufacturing, I am not an electrical or computer engineer, but I am very curious. I am aware of the heating problems this would cause considering an even more dense packing of transistors and the manufacturing problems considering you would have to laser etch through so much silicon, but unlike enlarging the size in width and height there wouldn't be problems with making the most of the circular silicon wafers, and unlike with that you would be keeping the parts very close which means it wouldn't slow down the speed of the electricity getting from one part of the processor to the other because the processor already has 1000s of transistors stacked horizontally and vertically.
I am curious if you could solve the heating problems by laying down thin intermittent heatsinking layers, while keeping the vertical throughput. And fix the manufacturing problems partially by using separately etched wafers every 10 layers or so. Could this be possible or are there lots of problems I'm not thinking of (and I'm sure there are)? Thanks.