For a CPU, you still need to address the transistors somehow. Chips aren't pure transistors, there are wires coming down from above, and that takes up a lot of

For a CPU, you still need to address the transistors somehow. Chips aren't pure transistors, there are wires coming down from above, and that takes up a lot of space. As a result, vertical density doesn't scale as you might hope. For example: https://en.wikipedia.org/wiki/Integrated_circuit#/media/File:Cmos-chip_structure_in_2000s_(en).svg https://en.wikipedia.org/wiki/Integrated_circuit#/media/File...