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07 July 2022

Mini-Transistors: Architects of the Greatest Technological Revolution of the 20th Century

Estimated reading time Time 5 to read

Although we are not aware of it, our daily lives are strongly influenced by an electronic device of microscopic size: the transistor, a device celebrating its 75th anniversary this year. Transistors are the essential components of the chips that pervade today’s world and that have become quite the hot topic in recent times due to their scarcity in the market for various reasons. In this article I shall demonstrate some particularities of these amazing electronic components. 

BBVA-openMind-Ignacio Martil-Mini-transistores-Figura 1-Microscope image of a modern field-effect transistor. The scale gives an idea of its minuscule size, although there are even smaller ones.
Microscope image of a modern field-effect transistor. The scale gives an idea of its minuscule size, although there are even smaller ones.


“Digital economy”, “digital banking”, “digital company transformation”, “digital terrestrial television”. Surely you have read or heard these and related expressions hundreds of times, almost daily.   And I am sure that the term “digital” is synonymous with new, current, cutting-edge, competitive, etc. You are not wrong, it is true to a large extent.

What you may not know is that the digital world is made possible by the existence of a tiny electronic device known as a transistor. You may also be unaware that you carry them in your pants pocket or in your handbag – billions of them work for you every day. With their help, you can talk to anyone you want; whether you’re in the next street or strolling down the main avenue in Melbourne or San Francisco, they allow you to have a phone conversation or video call with excellent sound and picture quality. Thanks to the transistors in your phone, photos of your children, partner, friends, etc. are with you at all times. They also work with your car’s GPS, your home or work computer, the TV where you watch your favorite series, maybe even your watch.

Los tres ganadores del Nobel de Física de 1956 /Imagen: Copyright © The Nobel Foundation
The three winners of the 1956 Nobel Prize in Physics /Image: Copyright © The Nobel Foundation

The transistor is at the heart of all the equipment and platforms that have driven the true revolution in technology, customs, and work and leisure habits in which we are immersed. With the help of transistors, in addition to making phone calls and sending emails, you can access the many social network apps (all those linked to the Internet: WhatsApp, Telegram, Facebook, Instagram, Twitter, etc.); thanks to the transistor, you can enjoy (or suffer) the contents of platforms such as Netflix, HBO, Amazon, Filmin, etc. The transistor is inside all the chips that enable the simple and convenient use of the aforementioned devices, applications and platforms. Simply put: without the transistor, the Internet would not exist.

The transistor is arguably the most important invention of the 20th century and is often reviewed as the quintessential example of how scientific research can lead to useful commercial products. It emerged in 1947 at Bell Telephone Laboratories, the research laboratories of a large U.S. telecommunications company (A. T. & T.), by three great scientists: William Shockley, John Bardeen and Walter Brattain


Today’s chips are only a few tenths of a square millimeter in size, and inside each one there are billions of transistors, so an immediate question arises: How is it possible to have such a huge number of transistors in such a small space? Well, because they are astonishingly small, since each one occupies a few tenths of a nanometer, a size similar to that of a protein or a virus. In other words, we do not see them, but they are with us every day, from the moment we get up to the moment we go to bed. The following figure shows one such device, on a comparative scale. I rest my case.

BBVA-openMind-Ignacio Martil-Mini-transistores-Figura 2 Comparando el tamaño de un transistor con la biología microscópica. Algunos dispositivos actuales, como el de la figura (su denominación técnica es FinFET), son tan pequeños como una proteína o un virus
Comparing the size of a transistor with microscopic biology. Some current devices, like the one in the figure (its technical name is FinFET), are as small as a protein or a virus.

The following figure shows what a current chip looks like when viewed under a microscope. Even with the magnification provided by this instrument, it is not possible to see the transistors inside.

BBVA-openMind-Ignacio Martil-Mini-transistores-Figura 3-Arriba: imagen de un chip, obtenida con un microscopio. Lo que se ve son las pistas metálicas de interconexión de los transistores que están debajo del entramado, que no son visibles. Abajo: detalle ampliado del cuadrado señalado en la parte superior. Aquí tampoco se ven los transistores
Above: image of a chip, obtained with a microscope. What can be seen are the metal interconnection tracks of the transistors underneath the lattice, which are not visible. Below: enlarged view of the square shown at the top. The transistors are not visible here either

Why are they so small? For many reasons, some of which are related to the historical evolution of the technology that makes them possible. In the following section, I shall examine this aspect, describing how the number of transistors included in chips has evolved up to the present day and detailing some of the reasons behind the quest for such a small size.


Gordon Moore, one of the founders of Intel (the world’s leading chip manufacturer) published a famous article in 1965 which, over the years, has become a kind of prophecy: the number of transistors on a chip doubles every two years.   This article, a real gem in the history of electronics, is probably one of the most influential in the subsequent development of this branch of science and technology. 

The increase in the number of transistors in chips has since followed this trend, which is known as Moore’s Law. This prediction has acted in the microelectronics industry as a kind of “self-fulfilling prophecy”, i.e. manufacturers have been determined to make it come true from one year to the next. Of course, this is not just to fulfill a prophecy, but to seek (and find) the benefit of this trend, which acts on the industry almost as a kind of “divine mandate”. When you read Moore’s article, you cannot help but be amazed that the predictions he made in it have not only been fulfilled, but have been fulfilled year after year for more than half a century. It is not easy to find in any other branch of industry the “pursuit” of a forecast with as much determination as this one. The following figure shows such a law:

BBVA-openMind-Ignacio Martil-Mini-transistores-Figura 4 Ley de Moore para procesadores (CPUs) y para memorias. La escala vertical es logarítmica.
Moore’s Law for processors (CPUs) and for memories. The vertical scale is logarithmic.

Such an enormous increase in the number of transistors in a chip has been possible thanks to the tremendous development of its manufacturing process, through the use of a compendium of truly amazing technologies.


Nowadays, chips have more and more transistors and this is only possible by reducing their size, which has advantages, albeit at the cost of increasing the complexity of the manufacturing process. The smaller the transistors, the smaller the chip itself, and the more chips fit on a single wafer. Meanwhile, the cost of processing a wafer remains roughly the same, regardless of how many chips can be obtained from each one.  This means that reducing the size of the components results in cheaper chips. Alternatively, chips can be kept the same size so that they have more transistors inside them. This makes them much more powerful but not (much) more expensive. On top of that, scaling down the transistors improves their performance without increasing their power consumption.

BBVA-openMind-Ignacio Martil-Mini-transistores-Figura 5 Técnico de una fábrica de circuitos integrados con una oblea de silicio procesada con multitud de chips
Technician at an integrated circuit factory with a silicon wafer processed with a multitude of chips.

In other words, there are strong incentives for chip manufacturers to reduce the size of their transistors. And that is exactly what they have been doing in the last few decades, where the number of transistors on a chip has increased from hundreds to billions, reducing its size to staggering dimensions, as we have already seen in the first figure of this article. Reducing the size of these already tiny devices is still the most reliable way to get more computing power out of the chip, because electrons flow faster and more efficiently through them.


At the beginning of this century, it was predicted that the end of Moore’s Law would come around 2015. The author of the prediction is Mark Lundstrom, a Purdue University professor who, throughout his career, often thought what many others in the industry thought, “This is the end”.   Lundstrom began working in the microelectronics industry in the 1970s and attended his first chip manufacturing conference in 1975. There he met Moore, whom he did not know. He recounts the following of that meeting:  

There was a guy named Gordon Moore giving a talk. He was well known within the technology community, but no one else knew who he was; I remember something he said in his talk, “Soon we’ll be able to put 10,000 transistors on a chip. What could someone do with 10,000 transistors on a chip?”

Today, there are chips on the market with more than 15 billion transistors. We could ask their designers and manufacturers what can be done with them today and what can be done in the near future: 5G telephony, Artificial Intelligence, Internet of Things… All these advances will continue to make use of increasingly more powerful chips with smaller and smaller transistors. In other words, transistors will continue to be with us in our lives and in the lives of our children and grandchildren, and who knows how long we will carry them in our pockets?

Ignacio Mártil

Professor of Electronics at the Complutense University of Madrid and member of the Spanish Royal Society of Physics

Author of the book Energía solar: De la utopía a la esperanza (Análisis y crítica)

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