If there are billions of transistors in a CPU, there is no chance that somebody designed every single one of them manually. Is their layout calculated or something?
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There are hierarchical layers of building blocks.
A silicon team designs a handful of different transistors for a given process.
Next level up someone is making building blocks like AND and OR gates, and D Flip flops out of transistors, hand designed.
You get enough of these building blocks with their attributes detailed enough, you can put them together into a library of gates.
Synthesis tools can compile higher level languages like verilog and vhdl into a netlist that uses the predefined building blocks.
Next layer up people will design reusable things like DMA controllers or CPUs in their chosen HDL.
Special useful blocks like 10gig ethernet Logic are probably hand designed and laid out from discreet transistors to make sure they perform at top speed.
Most of the design work is done at the top level module level, and complied down thru the layers.
Very few hand designed transistors in the chip..
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