This is why most "semiconductor" companies are actually fabless, focusing on design while working with a partner(like TSMC) to have their designs manufactured.
I remember hanging out with Carl Amdahl after we were pitched our nth fabless semiconductor company, and him making the joke that if he ever started another company making IC designs, this time he would call it Fabulous Semiconductor.
You wouldn't normally be physically manufacturing CPUs yourself.
Most likely you'd be supplying an "IP core", which is basically just software. More niche than that, if you actually wanted to supply physical chips, you would contract out the manufacturing to TSMC for example.