Not sure... logic fabs range from boring 3.3/5V HC CMOS range stuff (I think 200nm up to, yes, 2um fabs are still hacking away at silicon as far as I know) down to 50-200nm LVCMOS (3.3V max or thereabouts) and further (with the ~1V stuff being 20-100nm GHz stuff, and occasionally odd fancy things like Intel's FinGate stuff). These are all capable of analog circuits of modest to high speed, with the main downside that offset voltages (in diffamps and such) aren't generally all that well controlled, and references are hard to make (usually, a substrate-grounded BJT structure has to be half-assed into existence from N-wells and such, so a ratio of emitter areas and current densities can be used for a bandgap reference). On the upside, tall stacks of metal and SiO2 layers allow transmission lines and inductors of modest Q to be built (typically a Q peak of 10-20 in the 2-20GHz range), which makes power amplifiers and filters for low-GHz band circuitry feasible.
It would seem to me, as time goes on, the biggest fabs will also have to invest in the most diverse -- as well as the largest, most productive machinery and techniques -- to maintain their market share. Maybe they don't, and it's more than possible to thrive making only CMOS. But some examples of diversity (that I recall reading about, but don't really know how common they are in practice) include copper metallization, HfO2 gate oxide, ferroelectric gate oxide (i.e., turning DRAM into FeRAM), various coatings, passivations (Si3N4, etc.), platings (Au, Ni, ??) and various optimizations (supposedly, DRAM is hard to make in a general CMOS process, so MCUs rarely have it onboard, using SRAM even though it's expensive). Not to mention all the things needed to do MEMS, IR to UV optics, thermal and more. It's starting to look less like computers and more like "Periodic Table Smorgasbord-on-a-chip". Which is pretty amazing...
Apparently, fancy stuff like SiGe:C is even being used for boring parts like op-amps. When you rub together a few hundred 60GHz+ fT HBTs, you can get curiously low noise levels, while still achieving average or above-average GBW.
Tim
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