I've just started to read about layout (beginner) and I came across this in Baker's book,
As you can see in the above, the substrate connection is made with a p+ active region. This makes sense for a single NMOS. But what if I had another NMOS right beside this that I wanted to connect a different substrate voltage to (body biasing)? Is there no seperation between the two?
In other words, the substrate connection in the above doesn't seem to be restricted to just this device. What if I wanted to add another device with a different substrate voltage, how would that work since they both now share the p-substrate and hence the first device's substrate voltage? How do you isolate them?