Smartphones, computers, cars, home appliances — every one of these devices we use relies on semiconductors.

・In smartphones, they serve as processing chips (CPUs).

・In automobiles, they serve as power-control chips (power semiconductors).

・In cameras, they act as sensors that convert light into electrical signals.

A semiconductor is a material that can let electricity flow — or stop it — in just the right amount. This “just-right” quality is the key that supports modern society.

A semiconductor is:

“A material with properties in between a conductor (which conducts electricity well) and an insulator (which does not).”

・Conductor: Conducts electricity very well (e.g., copper, silver, aluminum)

・Insulator: Barely conducts electricity at all (e.g., glass, rubber)

・Semiconductor: Its ability to conduct electricity changes depending on conditions (e.g., silicon, germanium)

The defining trait of a semiconductor is that the way electricity flows through it changes in response to external conditions.

・As temperature rises, electrons move more freely, increasing conductivity.

・When exposed to light, electrons become excited and a current flows (as in optical sensors).

・Applying voltage allows current to be controlled (as in transistors).

Because a semiconductor “senses its environment and responds,” it is ideally suited for sensors and switches.

The flow of electricity arises from the movement of electrons (negative) and holes (positive vacancies).

・Electron (e⁻): A particle carrying negative charge.

・Hole: A positive vacancy left behind when an electron departs.

By changing the number of these electrons and holes, the material’s electrical conductivity can be freely controlled. This process is called “doping” (covered in detail in the next chapter).

When people think of semiconductors, silicon comes to mind first. There are three main reasons:

1.It is abundant on Earth and inexpensive to obtain.

2.Its crystal structure is stable, making it well suited to precision processing.

3.It can form an oxide layer, giving it excellent insulating properties.

Because silicon is easy to work with, offers high performance, and is low in cost, it remains the primary material used today. It is this element’s name that gave rise to the term “Silicon Valley,” the nickname for the heart of the American IT industry.

・Information processing: Processing chips such as CPUs and GPUs

・Communications>: Communication control in smartphones, 5G base stations, etc.

・Energy: Solar cells, power semiconductors for EVs

・Medical: Biosensors, diagnostic equipment

・Industrial equipment: Robotics, automation systems

Semiconductors are often called “the rice of industry” — a foundational technology that touches nearly every industry.

・The evolution of computers is determined by the evolution of semiconductors.

・Achieving a decarbonized society requires high-efficiency power semiconductors.

・The advancement of AI-driven society depends on high-performance memory and processing devices.

In other words, semiconductor technology is what determines a nation’s technological and economic strength.

Semiconductors are “an invisible presence that drives everything.” Smartphones, automobiles, and AI all ultimately rest on a foundation of semiconductors. It could be said that our research, development, and manufacturing work is, in effect, designing the very mechanisms of society itself.

・A semiconductor has properties intermediate between a conductor and an insulator.

・It is a control material whose electrical behavior can be changed depending on conditions.

・Silicon remains the mainstream material, but new materials such as GaN and SiC are also emerging.

・It is the heart of modern society, supporting every industry.

1.How does the conductivity of a semiconductor change?

2.Why is silicon the leading material?

3.How would you describe the social significance of semiconductors in one sentence?

Column Supervisor: Koji Kakumoto (Otis Group Co., Ltd.)

After studying abroad and working in planning and development at a trading company, he joined Otis Group Co., Ltd. in 2011. While primarily working in the Corporate Planning Department, he has also served concurrently in manufacturing and technical divisions, and since 2018 has served as Representative Director, working to drive business growth and strengthen the organization.

This article is a general technical explanation intended for educational purposes and does not refer to any specific company, product, or technology.