Quantum effects, particle physics, and then the unknown (for now).

10, 7 and 5 nm patterning and EUV light sources are basically magic.

I'd say the field effects on electrical flow are probably the weirdest part to look at, and they don't reach 'magic' levels.

The atoms below that are relatively straightforward, and them being made up of building blocks is fine I guess, increasingly irrelevant to the issue of a computer.

And going up everything starts to get very non-magical as you turn response curves into binary signals and then string gates together.

Qm is still magical as you sort of use it but do not really understand it. It is so weird. And that is magically part.

Btw I read your below word as above.

It's such a narrow sliver of quantum effects that are relevant here, though, and it's not the weird stuff.

Quantum tunneling is a step into weird.

You don't need tunneling to make a transistor work.

(And for difficulty making walls too thin lest electrons leak through, you don't need to invoke tunneling to explain that.)

i think amplified current flow through bipolar junction collector depletion zones are the weirdest part, and they are magic.

Yeah for me it is the parasitic bjt/collector that forms in a fet (c.f. latch up). Also that bjts work in reverse active to some extent, despite the emitter nominally being the injector of the carriers. Weird!

Also I never understood things like slew rates, noise, gain bandwidth. Too high up the stack.

Gain bandwidth is directly related with slew rate. Slew rate is mostly an effect of capacitances (gate capacitance in FETs for example.) Noise is mostly caused by thermal effects (atoms bumping randomly.)