On October 8, 1926, an Austrian-Hungarian physicist named Julius Edgar Lilienfeld — recently emigrated to the United States, working out of a Brooklyn lab — filed a patent describing a device that shouldn't have existed for another two decades. It was granted January 28, 1930, as US Patent 1,745,175: "Method and Apparatus for Controlling Electric Currents."

The invention was, in plain language, a field-effect transistor.

Lilienfeld's device sandwiched a thin film of semiconductor material (he suggested copper sulfide) between a source and drain electrode, with a third "control" electrode placed nearby but electrically insulated. Applying a voltage to the control electrode created an electric field that swept charge carriers through the semiconductor channel — modulating the current between source and drain without the control electrode ever drawing current itself.

That is exactly how every MOSFET in your phone, laptop, and car works today. Lilienfeld described it in 1926.

He filed two follow-up patents — US 1,877,140 (1932) and US 1,900,018 (1933) — refining the geometry and materials, including a version that looks remarkably like a modern thin-film transistor. And then… nothing. Lilienfeld never built a working prototype. He couldn't. The semiconductor materials of the 1920s were riddled with surface states and impurities that trapped charge carriers and killed the field effect before it could do useful work. The physics was right; the metallurgy was a generation away.

Here's where the story gets extraordinary. In December 1947, Bardeen, Brattain, and Shockley at Bell Labs demonstrated the point-contact transistor — but they had originally been trying to build something much closer to Lilienfeld's field-effect device. Shockley's team went to file their patent and were told, essentially, "you can't." Lilienfeld's 1926 patent claims were broad enough that Bell Labs' patent attorneys had to carve carefully around them. That's part of why the world got the bipolar junction transistor first — it was patentable in a way the field-effect device wasn't.

The MOSFET, when Mohamed Atalla and Dawon Kahng finally built one in 1959, was essentially a vindication of Lilienfeld's 33-year-old drawings. The breakthrough that made it work was the silicon dioxide gate insulator — the missing material that Lilienfeld's copper sulfide films couldn't approximate.

Why it matters now:

• Every MOSFET ever manufactured — and there have been more of them made than any object in human history, roughly 10²² — is a descendant of Lilienfeld's insulated-gate topology.
• Modern thin-film transistors (TFTs) driving every OLED and LCD pixel are almost geometrically identical to Lilienfeld's 1933 patent drawings.
• The current push toward 2D-material transistors — MoS₂, WSe₂, graphene FETs — is arguably closer to Lilienfeld's original copper-sulfide vision than the silicon MOSFET ever was.

Lilienfeld died on the Virgin Islands in 1963, largely forgotten. The American Physical Society named its highest condensed-matter prize after him in 1988. Every time you tap a screen, roughly a billion Lilienfeld-descendant switches flip to render the response.