Vespula: which mega brand out there thinks that inverter speed is key to their needs over needs?

Each and every mega brand will think so, because the inverter (or NOT gate) is at the very heart of digital logic. In theory, you need just two basic elements for digital logic: AND gate and NOT gate (inverter). You can build everything from AND and NOT, so it is pretty fundamental.

Here's introductory material featuring some of the technical vocabulary you can see now and then on this forum, like n- or p-type transistor, MOS, CMOS, inverter etc.:

Digital Logic Structures