Who really invented the transistor, and who was left off the patent?

Bardeen, Brattain and Shockley of Bell Labs get the credit, but a patent for the field-effect transistor principle had been filed in 1925, and in 1948 two researchers in France applied for a patent on their own device, which the standard history describes as an independent parallel development.

The earlier patent belonged to Julius Edgar Lilienfeld, who filed in Canada on 22 October 1925. He published no research articles, his work was ignored by industry, and he was never able to build a working practical device. In 1934 Oskar Heil patented another field-effect transistor. Work in the 1990s showed that one of Lilienfeld's designs worked as described and gave substantial gain.

At Bell Labs, Shockley's team first tried to build a field-effect transistor and failed because of problems with surface states. Trying to understand that failure led them instead to the bipolar point-contact and junction transistors. On the afternoon of 23 December 1947, Brattain and H. R. Moore demonstrated a point-contact germanium transistor working as a speech amplifier with a power gain of 18, a date often given as the birth date of the transistor.

Then came a quarrel. Shockley was shocked that the device was credited to Brattain and Bardeen, who he felt had built it "behind his back". Bell Labs lawyers found that some of his own writings on the transistor were close enough to Lilienfeld's 1925 patent that they thought it best to leave his name off the patent application. Meanwhile, Herbert Mataré and Heinrich Welker, working in France, applied for a patent on their own "Transistron" on 13 August 1948. As Bell Labs had not announced its transistor before June 1948, it was an independent parallel development.