Home-made semiconductor fabrication techniques are getting more sophisticated. From the hacker who put 6 transistors on a chip in an amplifier configuration, behold, one thousand two hundred transistors.
https://www.youtube.com/watch?v=IS5ycm7VfXg
(Admittedly, not configured as anything in particular yet, but the work is getting there. He's already half-way to an Intel 4004. I'm willing to bet that you can make a viable CPU with 1200 transistors if it used a bit-serial micro-architecture.)
Blog article is here: http://sam.zeloof.xyz/second-ic/