I worked at a company that was vertically integrated. The fab was across the road from where ASICs were designed. The last technology node, I believe, was 130

I worked at a company that was vertically integrated. The fab was across the road from where ASICs were designed. The last technology node, I believe, was 130nm on 6" wafers. To go the next step would have cost something like $1B in 1990s dollars. That's a tall order for an in-house fab; if you're going to spend that kind of money the fab had better be doing something all the time. So either you take on foundry work, or you get rid of the fab and farm out your work to a foundry elsewhere. As far as I know, the same thing happened up the food chain; the company that did make our next ASICs (IBM, Essex Junction Vermont) has spun off that fab as well. So it goes.