Sam Zeloof (sam.zeloof.xyz) has been working in the area of DIY semiconductor fabrication, and has successfully fabricated working ICs (from 6 - 100 transistors). He’s done an incredible job at reaching ~1970’s technology levels in a home lab.

Another example of DIY fabrication: hackaday.com/…/jeri-makes-integrated-circuits/ Jeri Ellsworth made her own silicon inverter.

These examples are still very small-scale compared to even simple microprocessors, etc - but it’s fascinating to see this level of technology becoming more accessible.