New generation memory chips promise to cut energy use

• Author: Catherine Jewell, Yuka Okakita and Tomomi Taguchi
• Position: Information and Digital Outreach Division, WIPO/WIPO Japan Office

Dr. Yamazaki in a briefing with a team of researchers on SEL’s state-of-the-art supercomputers, which enable the company to perform complex, largescale simulations at high speed. (Photo: Courtesy of SEL)

Tell us about the current focus of SEL’s work and how it supports global environmental goals

I have been working in the field of semiconductors for several decades, ever since I invented and patented what is known as flash memory (patent no. JP 886343), at the age of 28 in 1970. Flash memory is embedded in most of the electronic devices we use every day. Essentially, it makes it possible to store data and information even when the device is turned off. Flash memory is also the least expensive form of semiconductor memory or data storage. I never dreamed that the silicon large-scale integration (Si LSI) – which made it possible to make computer chips so powerful in terms of their micro-processing and data storage capacity – would be so widespread, nor that it would contribute to global warming because of its high-power consumption.

In 2009, we found a new crystal structure of oxide semiconductors (CAAC structure), which makes for more energy-saving computer chips or LSIs. For more than 10 years, now, we have been conducting intensive R&D to improve the performance of LSIs to reduce the power consumed by data centers and supercomputers.

Our goal is to make semiconductors more energy efficient. Through our pioneering work, we have developed a new semiconductor material with high current retention characteristics. An Si FET has a leakage current of around 10^-12A/µｍ when turned off; on the other hand, an OS FET (crystalline oxide semiconductor field-effect transistor) has an extremely low off-state current of 10^-24A/µｍ. That means that data can be retained for a long time. By taking advantage of these high current retention characteristics and silicon’s good electrical properties, we have developed a new Si/OS composite structure. By utilizing their combined synergistic effect, we aim to create semiconductor devices with greater power-saving properties that could be achieved by silicon technology alone. Broad uptake and use of this new technology will greatly contribute to the fight against global warming.

For those who are not familiar with semiconductors, can you say a few words about the role they play and their importance in the modern world?

All the electronic devices we use every day, our smartphones, laptops, televisions, computers...