What Is a Semiconductor? - Devices, Properties & Fundamentals

Instructor: Paul Zandbergen

Paul has a PhD from the University of British Columbia and has taught Geographic Information Systems, statistics and computer programming for 15 years.

Microchips used in computer systems use a very thin sheet of silicon dioxide with microscopic electronic circuitry. Silicon is a semiconductor material, which means the material can be altered to either conduct an electrical current or not.


The central processing unit (CPU), or microchip, of a computer contains a large number of transistors. Transistors are like microscopic switches that control the flow of electricity based on whether the switch in open or closed. A transistor, therefore, contains only binary information: a 1 if a current passes through it (the switch is closed) and a 0 if a current does not pass through it (the switch is open). Transistors are made of semiconductor material. A semiconductor is a material that can be altered to either conduct an electrical current or to block its passage. The most widely used semiconductor in microchips is silicon. This material gave Silicon Valley its name. Silicon Valley is the region just to the south of San Francisco where many of the major companies in the computer industry had their start and where many of the new start-up companies are also located.

Semiconductor Technology

A very thin piece of silicon dioxide is used as the base material for building a microchip. This is called a wafer, or a slice. Microscopic electrical circuits are etched into this sheet using a system of light, light-sensitive films and acid baths. These circuits form the transistor switches used to process binary information. The slice itself is embedded in a piece of plastic or ceramic material. The ends of the circuitry are attached to metal leads that connect the microchip to other components.

Example of a silicon wafer
silicon wafer

Manufacturing Microchips

The electronic circuitry is very small. This requires that the semiconductor material is very pure. Microchips are, therefore, fabricated in very clean facilities known as cleanrooms, since even minor contamination from the air can introduce defects.

To make computers faster, microchip engineers try to make the circuitry as small as possible. This means more transistors can be placed onto a single silicon wafer. More transistors mean more processing power. Small circuitry also means the time it takes for an electrical current to travel through the transistors is shorter. This makes for faster processing.

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