The transistor itself is composed of a single phosphorous-31 isotope, which has been precisely placed on a base of silicon using a Scanning Tunneling Microscope in an ultra-high vacuum chamber.
These robots--whether designed to cut your grass or merely to keep you entertained--are luxury items, and with the exception of the relatively inexpensive Roomba robotic vacuum, they are owned mainly by hobbyists and high-end gadget enthusiasts.