Claude Paillard, F2FO, has put together a fantastic video of
making a homebrew triode vacuum tube. See the video at the
bottom of this page.
OK, he has a few pieces of equipment you don't find in every hamshack,
like a simple spot welder and laboratory glass blowing gear.
After you watch this video, you will probably crave the little
spot welder for all sorts of projects.
It seems like making vacuum tubes (valves) might be a lot
simpler (at least possible) compared to a homebrew transistor.