As transistors improve, they enable new capabilities such as computing and high-speed communication, the Internet, smartphones, memory and storage, robotics, artificial intelligence, and other capabilities that have not yet been imagined. Semiconductor technology does not face the same material and energy constraints as other technologies. And the less material they use by shrinking, the faster, more energy efficient, and more capable they become.
In the short term, it is relatively clear how we will continue to improve transistor technology, but it becomes murkier as we move further away from today. The basic planar (2D) MOSFET structure remained unchanged from 1960 until around 2010, when further increasing transistor density and lowering power consumption became impossible. The first 3D MOSFET, the FinFET, transformed the flat and wide transistor structure into a tall and narrow one.
The FinFET is also known as a thin-body MOSFET, a concept that has influenced the development of new devices. It was inspired by the realisation that current would not leak through a transistor within a few nanometers of the silicon surface because the surface potential is well controlled by the gate voltage.
From such 3D transistors to 3D-stacked transistors, 3D monolithic circuits, and multichip packaging, the 3D thin-body trend will continue. Monolithic 3D logic ICs will most likely begin modestly, by stacking the two transistors of a CMOS inverter to reduce the footprints of all logic gates.
The thin-body trend may reach its apex in 2D semiconductors, where thickness is measured in atoms. Engineers in California and Texas demonstrated a MOSFET with a critical dimension: a gate length of just 1 nanometer across in 2016. Even with a gate as small as 1 nm, the transistor leakage current was only 10 nano amperes per millimetre, which is comparable to today’s best production transistor.
The advancement of transistor technology hasn’t been uniform or smooth. In the distant future, the entire transistor could be prefabricated as a single molecule.
