# The 3-D Transistor Transition ![rw-book-cover](https://readwise-assets.s3.amazonaws.com/static/images/article3.5c705a01b476.png) ## Metadata - Author: [[The Asianometry Newsletter]] - Full Title: The 3-D Transistor Transition - Category: #articles ## Highlights - For decades, the semiconductor industry's building block was the Metal-Oxide Semiconductor Field Effect Transistor or MOSFET. This transistor is very common in digital circuits like inverters, NAND gates, and SRAM cells. It is made up of a gate sitting on top of a channel connecting a source and a drain. The source and the drain are basically just regions of silicon doped with the atoms of other elements to donate or receive electrons. ([View Highlight](https://read.readwise.io/read/01h5v9hh818vhxg9g9wefwdcdb)) - As the transistor's physical dimensions shrinks, the source and the drain gets closer and closer together. The insulating layer between the gate and channel gets thinner - 1.2 nanometers at one point or 5 atoms wide. And the channel itself gets thinner, as well. With that, the gate's control over the current's flow from the source to the drain gets weaker. And what basically then happens is that the current "dives under the gate" as it goes from the source to the drain. Like a rabbit burrowing into a farmer's vegetable patch, current can now sneak from the source to the drain even if the gate is closed. It can travel through the part of the channel furthest away from the gate, or in some circumstances even through the silicon substrate itself. This is called the "short-channel effect" and by the mid-1990s - the 350 nanometer process node - it was becoming a serious industrial concern. ([View Highlight](https://read.readwise.io/read/01h5v9mjsmsp91ew5z5s3p63wy)) - The way things were going, transistors would consume as much energy in their "off" state as they did during their "on" state. This came at a time when consumer electronics started to get more portable, leading to higher demands on power efficiency. Researchers soon realized that they were fighting a losing battle. The classical MOSFET structure had a final end point - a practical, final size limit at about the 20 nanometer mark. Nobody saw a path to extend this final runway. In 1996, with the leading edge at 250 nanometers, DARPA became aware that the industry did not have a long term plan beyond the year 2002 - 5 years away. They called for proposals of research on sub-25 nanometer devices, titled the 25-nm Switch. ([View Highlight](https://read.readwise.io/read/01h5v9njw6vy5d4h5czp21vqj2))