What is a semiconductor?

Substances that conduct electricity are known as conductors, while substances that do not are known as insulators. Semiconductors have unique properties that apply to both, meaning that under certain conditions they can conduct electricity and under others, they can resist it. This unique classification makes semiconductors ideal for technologies such as computer chips, artificial intelligence (AI) chips and Internet of Things (IoT) devices that depend on conducting a large amount of power through a small area. 

In most modern technologies, semiconductors act like tiny electrical switches, turning off and on repeatedly to enable the flow of electricity. A semiconductor’s conductance—the ease or difficulty with which an electric current flows through it—varies depending on current and voltage.

Semiconductors are widely used across many industries, including personal computers (PCs), home electronics, automotive, industrial manufacturing and more. According to a recent report by the Semiconductor Industry Association (SIA), semiconductor sales have increased from USD 139 billion in 2001 to USD 526 billion in 2023. This growth represents a compound annual growth rate (CAGR) of 6%.¹

The semiconductor industry’s rapid rate of innovation can be largely attributed to Moore’s law—the rule that the speed and capability of computers double every two years. In the semiconductor industry, Moore’s law applies to the number of transistors that a microchip must contain to keep up with the growing demands of computing devices. Leading manufacturers continually seek ways to double transistor counts biennially, ensuring advancements in semiconductor technology.

Most semiconductors are made of crystals because of their unique atomic properties. Whereas most common conducting elements have a single electron in their outermost shell, semiconductors have four. This, and other factors, make semiconductor crystals (typically silicon) perfect for controlling the electrical currents that underpin complex, modern technological devices.

To control the flow of electricity through electronic circuits and devices, engineers manipulate the flow of electrons through semiconductors by creating regions with positive and negative charges, a process known as doping.

In the production of semiconductors, doping is a process where impurities, also known as impurity atoms, are intentionally introduced to a semiconductor’s crystal lattice to modify its electrical properties. By introducing dopant atoms, engineers can make the material more or less conductive. There are two kinds of doping: N-type and P-type.

• N-type doping: N-type doping is where engineers add elements with more valence electrons than the host material. This change increases the number of free charge carriers in the atom, making the semiconductor material more conductive than it was previously.

• P-type doping: P-type doping also makes material more conductive, but by using a slightly different method. In P-type doping, elements with fewer valence electrons than the host material are added, creating what’s known in computer science as a “hole”: a place that’s missing electrons that typically carry charges and increase conductivity.

Semiconductors are typically classified into two main types: intrinsic and extrinsic. Here’s a closer look at their differences.

• Intrinsic semiconductors: Intrinsic semiconductors are semiconductors that are made of a single, pure material that hasn’t been manipulated in any way. Intrinsic semiconductors are often called ‘elemental’ semiconductors, as many of them are well-known elements on the periodic table, such as carbon, boron, silicon and germanium.

• Extrinsic semiconductors: Extrinsic semiconductors are semiconductors that have undergone doping, intentional contamination to alter a material’s conductivity. Radio frequency (RF) semiconductors, for example, are considered extrinsic because they combine materials like gallium arsenide (GaAs), gallium nitride (GaN) and silicon (Si) that make semiconductors work at higher radio frequencies.

Semiconductor devices are electronic components that use conductors and insulators to control the flow of electric currents. The most popular kind of semiconductor device is the widely used transistor, a small, durable, electronic component that powers most modern electronics.

Until transistors were invented in 1947, vacuum tubes were widely used for the same purpose. Transistors proved more compact and efficient than vacuum tubes and quickly replaced them. Today, transistors are used in a wide range of devices, including computer chips, microprocessors, cars, robotic devices and more. Transistors are highly flexible; in addition to acting as conductors and insulators, they can act as switches, amplifiers and rectifiers as well.

• Switches: Components in semiconductor devices that are turned on or off to control the flow of an electric current.

• Amplifiers: Circuits that increase the magnitude of an input signal in an electronic device.

• Rectifiers: Rectifiers, or rectifier diodes, are small semiconductor devices that convert electric currents from alternating current (AC) to direct current (DC) by allowing electricity to flow in one direction.

Semiconductors are manufactured in foundries, which are highly specialized companies that focus exclusively on semiconductor manufacturing, leaving design and distribution to others. Due to a range of factors, most of the foundries in the world are in Taiwan.

Today, 60% of the world’s semiconductor chips and more than 90% of advanced chips are made on the relatively small island of Taiwan.² Taiwan’s highly skilled workforce, invention of the foundry model of making semiconductors, and other factors have led to its near-total dominance of the semiconductor market.

Perhaps the best-known foundry in the world is the Taiwan Semiconductor Manufacturing Company (TSMC), founded in 1987, which produces the most advanced chips in the world for customers like Apple and NVIDIA. 

Today, TSMC’s dominance in the semiconductor market has made it a crucial part of the global supply chain for semiconductors. As a result, Taiwan has become a geopolitical focal point in the foreign policy strategies of major nations like China and the United States.

Semiconductors are made through a rigorous process known as wafer fabrication, or wafer fab, that begins with the slicing of semiconductor material into a thin segment. Silicon wafers are the most common wafers, but they are also made from gallium arsenide, silicon carbide, germanium and more.

After the wafer has been created, it is polished and ground through a series of different, highly specialized machines and an integrated circuit (IC) is installed on its surface through four highly involved steps.

• Step 1. Oxidation: Before an IC can be installed, a wafer must be precleaned with highly pure, deionized water. Some kinds of wafers, silicon wafers especially, are heated during this step and exposed to pure oxygen, a method known as thermal oxidation.

• Step 2. Masking: During the masking part of semiconductor manufacturing, photomasks—highly precise stencils—are used to create patterns on the wafers, a task known as photolithography. Each mask is critical in defining the circuitry of the semiconductor and how effectively it operates as an IC.

• Step 3. Etching: In the etching part of the manufacturing process, unnecessary material is removed from the wafer to give it an intentional pattern or shape. Like masking, etching is important to the establishment of ICs and other kinds of devices with a specific purpose that must be attached to the surface of the wafer.

• Step 4. Doping: Finally, extrinsic semiconductor materials are created by adding impurities to their crystal structure to change their electrical properties. Compounds used during this step include gallium arsenide, indium antimonide and many kinds of oxides.

In the last 75 years, semiconductors have become foundational to many modern technologies. From the early age of computing through the spread of the Internet, social media, mobile technology and AI, they have played a critical role in enabling electronic devices to function. Here are some of the most important semiconductor benefits.

Semiconductors enable the use of most modern electronic devices and therefore have use cases that span many industries. Here are some of the most common.

Semiconductors and semiconductor devices like integrated circuits (ICs), sensors and semiconductor chips are widely used in many different consumer electronic devices. From smartphones and laptops to smart home appliances, virtual assistants, TVs and more, semiconductors underpin technological devices that most consumers have come to depend on in both their private and professional lives.

Today’s cars use many features people have come to expect from their smartphones and PCs, like voice recognition, wireless connectivity and the ability to stream different kinds of media. Semiconductor chips underpin the technologies cars use to allow these features, letting passengers access the internet, have voicemails and text messages read aloud to them, receive directions, and more.

Semiconductors and semiconductor chips have become crucial in the medical field, essential to the operation of a wide range of medical devices and applications. Semiconductors power devices that enable medical imaging, diagnostics, patient monitoring and more, allowing critical data that helps improve patient treatments and outcomes to be transmitted in near real-time.

Smart manufacturing, also known as Industry 4.0, is the integration of new digital technologies like the Internet of Things (IoT), AI and cloud computing into manufacturing processes. In smart manufacturing, semiconductors and semiconductor chips power advanced sensors, embedded software and robotics that collect and analyze data in a factory setting, helping to streamline outdated, inefficient processes.