The surface-barrier transistor is a type of transistor developed by Philco in 1953 as an improvement to the alloy-junction transistor and the earlier point-contact transistor. Like the modern Schottky transistor, it offered much higher speed than earlier transistors and used metal–semiconductor junctions, but unlike the schottky transistor, both junctions were metal–semiconductor junctions.

A transistor is a semiconductor device used to amplify or switch electrical signals and power. It is one of the basic building blocks of modern electronics. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Some transistors are packaged individually, but many more in miniature form are found embedded in integrated circuits. Because transistors are the key active components in practically all modern electronics, many people consider them one of the 20th century's greatest inventions.