A transistor is a semiconductor device used to switch or amplify electronic signals and electrical power. The term transistor was coined by John R. Pierce as a contraction of the term transresistance. The Nobel Foundation states that the term is a combination of the words "transfer" and "resistor".

Bipolar transistors

A bipolar transistor is a type of transistor that is current-controlled and uses both electron and hole charge carriers. In contrast, unipolar transistors, such as field-effect transistors, are voltage-controlled and only use one kind of charge carrier.

Bipolar point-contact transistor

The bipolar point-contact transistor was the first type of transistor ever constructed. It was developed by research scientists John Bardeen and Walter Brattain at Bell Laboratories in December, 1947. They worked in a group led by physicist William Shockley. On December 16, 1947, Bardeen and Brattain applied two closely-spaced gold contacts held in place by a plastic wedge to the surface of a small slab of high-purity germanium. The voltage on one contact modulated the current flowing through the other, amplifying the input signal up to 100 times. On December 23 they demonstrated their device to lab officials - in what Shockley deemed "a magnificent Christmas present."

In 1948, the point-contact transistor was independently invented by two German physicists, Herbert Mataré and Heinrich Welker, working in Paris.

The point-contact transistor was commercialized and sold by Western Electric and others but was soon superseded by the bipolar junction transistor, which was easier to manufacture and more rugged. As of 2012 germanium point-contact diodes continued to be available for use as radio-frequency detectors. Point-contact diodes are made of other materials, including silicon, and have good microwave properties.

Bipolar junction transistor (BJT)

The BJT was Invented by William Shockley at Bell Labs on June 23, 1948, six months after the first bipolar point-contact transistor [1].

On February 13, 1948, John N. Shive, built a point contact transistor with bronze contacts on the front and back of thin wedge of germanium, proving that holes could diffuse through bulk germanium and not just along the surface as previously thought. Shive's invention sparked Shockley's invention of the junction transistor. William Shockley filed the original patent for the junction transistor on June 26, 1948, and it was issued, in part, as patent 2,569,347 on Sept 25, 1951[2]. The first BJT, grown-junction germanium transistor, was prototyped in 1949. Bell Labs announced Shockley’s grown-junction transistor on July 4, 1951[3]. This type of transistor with a layer or 'sandwich' structure went on to be used for the vast majority of all transistors into the 1960s, and evolved into the bipolar junction transistor.

On September 12, 1958, Jack Kilby of Texas Instruments built a circuit using germanium mesa p-n-p BJT slices he had etched to form transistor, capacitor, and resistor elements. Using fine gold "flying-wires" he connected the separate elements into an oscillator circuit. One week later he demonstrated an amplifier. T.I. announced Kilby's "solid circuit" concept in March 1959 and introduced its first commercial device in March 1960, the Type 502 Binary Flip-Flop priced at $450 each. However the flying-wire interconnections were not a practical production technique and only a few dozen units were shipped to customers for evaluation purposes

Silicon transistor

Transistors had all been made with germanium for the first six years of their existence. Silicon transistors became possible after Dupont began supplying high-purity "semiconductor-grade" material. In January 1954 Bell Labs chemist Morris Tanenbaum fashioned the first silicon transistor using a variation on Morgan Sparks and Gordon Teal's grown-junction technique.

But the Labs did not pursue the process further, thinking it unattractive for commercial production, which allowed Texas Instruments (TI) to claim credit for this breakthrough several months later. Having left Bell Labs to organize a research lab at TI, Teal hired a team of scientists and engineers led by chemist Willis Adcock to work on silicon transistors. Employing high-purity Dupont silicon, they made their first successful silicon BJT - an n-p-n structure using the grown-junction technique - on April 14, 1954. The 2N709 (FT-1310) n-p-n device was introduced in July 1961 as the first silicon transistor to exceed germanium speed.

Field-effect transistor (FET)

On October 22, 1925, Julius E. Lilienfeld filed a patent in Canada titled "Method and Apparatus for Controlling Electric Currents". He proposed a three-electrode structure using copper-sulfide semiconductor material. Lilienfeld also filed identical patents in the United States in 1926 and 1928. Today this device would be called a field-effect transistor.

In 1934, German electrical engineer and inventor Oskar Heil filed a patent in Europe on controlling current flow in a semiconductor via capacitive coupling at an electrode - essentially a field-effect transistor.

Junction gate field-effect transistor (JFET)

The junction field effect transistor (JFET), have a pn junction gate, is a non-insulated-gate FET. JFET was first proposed by William Shockley in Nov. 1952. The first demonstration was made the following year by Dacey and Ross.

In 1959, the planar method or manufacturing JFET was filed for a patent by Dr. Jean Hoerni at Fairchild Semiconductor. Major advacedments in JFET fabrication did not occur untile the 1970s, due to the large popularity of BJT. The use of JFET remained limited to specific applications with the introduction of MOSFET.

Planar process

In 1959, the first planar transistor (silicon JFET) was developed by Dr. Jean Hoerni[4][5] at Fairchild Semiconductor. The planar process used to make transistors made mass-produced monolithic integrated circuits possible. Fairchild introduced the 2N1613 planar transistor commercially in April 1960[6] and licensed rights to the process across the industry. The billion-transistor integrated circuits of today rely on Hoerni's breakthrough idea. One historian has called it "the most important innovation in the history of the semiconductor industry."

Challenged by patent attorney John Ralls to identify other uses for Hoerni's planar process, Fairchild co-founder Robert Noyce conceived the idea for a monolithic integrated circuit (IC) using metal-over-oxide interconnection scheme eliminating the "flying-wire" connections. This would yield a practical method of manufacturing Jack Kilby's solid circuits. (Jack Kilby's integrated circuit was based on germanium and flying-wire, while Robert Noyce's integrated circuit was based on silicon, planar process, and metal-over-oxide interconnection.) Noyce filed his "Semiconductor device-and-lead structure" patent in July 1959 and a team of Fairchild engineers (Jay Last et al.) produced the first working planar monolithic ICs in May 1960.

Metal–oxide–semiconductor field-effect transistor (MOSFET) and CMOS

The MOSFET, originally called the insulated-gate FET (IGFET), was achieved by M. M. (John) Atalla and Dawon Kahng at Bell Labs in 1959.

Investigating thermally grown silicon-dioxide layers, they found the surface states, which block electric fields from penetrating into the semiconductor material, could be markedly reduced at the interface between the silicon and its oxide in a sandwich comprising layers of metal (M - gate), oxide (O - insulation), and silicon (S - semiconductor) - thus the name MOSFET.

The MOS transistor conducting region is either p-type (making it a "p-channel" or pMOS) or n-type ("n-channel" or nMOS) material.

Fin field-effect transistor (FinFET)
Fully depleted silicon on insulator transistor (FD-SOI)

Power transistors: IGBT and MOSFET

Insulated-gate bipolar transistor (IGBT)
Double-diffused MOSFET (DMOS)

Process Technologies

Front-end-of-line (FEOL)

FEOL processing refers to the formation of the transistors directly in the silicon. FEOL generally covers all processes up to (but not including) the deposition of metal interconnect layers.

Back-end-of-line (BEOL)
  • Contacts
  • Redistribution layer (RDL)
  • Microbump

Moore's Law


  1. Morris, Peter Robin (1990). "4.2". A History of the World Semiconductor Industry. IEE History of Technology Series 12. London: Peter Peregrinus Ltd. p. 29. ISBN 0-86341-227-0.
  2. Proceedings of the IEEE, January 1996, p191-217)
  4. US 3025589 Hoerni, J. A.: "Method of Manufacturing Semiconductor Devices” filed May 1, 1959
  5. US 3064167 Hoerni, J. A.: "Semiconductor device" filed May 15, 1960
  6. Transistor Museum, Fairchild 2N1613,