From "Energy-Creation" to "Energy-Saving"

Aiming for Next-Generation Ultra-Low-Power Devices

Oxide semiconductors (OS) are attracting attention as next-generation semiconductor materials. Especially, we have focused on IGZO, a crystalline oxide of indium (In), gallium (Ga), and zinc (Zn), and pioneered research and development in this field. From this work, we have found two new crystal structures for OS: c-axis aligned crystal (CAAC®) and nanocrystal (nc-OS®).

These technologies are widely used in practical applications, starting with their use in the displays of smartphones manufactured by Sharp Corporation in 2012. Currently, we are working on the development of ultra-low power devices with the aim of practical application of crystalline oxide semiconductor technology in the LSI field.

>>>The detail of CAAC-OS

The Hidden Potential of a Crystalline OS
Unique Characteristics: the Key to Realize New Generation Devices

Five characteristics of crystalline oxide semiconductor

[1] Kiyoshi Kato et al.,“ 5291-ppi OLED Display Enabled by Monolithic Integration of C-axis-aligned Crystalline IGZO FET and Si CMOS,” IDW ‘21 Proc., 177 (2021).
[2] H. Kunitake et al.,“ A c-axis-aligned Crystalline In-Ga-Zn Oxide FET with a Gate Length of 21 nm Suitable for Memory Applications,” J. Electron Devices Soc., 7, 495 (2019).
[3] Reprinted with permission from A. Suzuki, et al. , ECS Trans., 2020 vol. 98, No. 7, pp. 13-27, Copyright (2020), The Electrochemical Society

Ultimate Switch can be Realized!
Ultra-Low Off-State Current of Crystalline Oxide Semiconductor

The OSFET can be considered to be an excellent "switch," as it has a very high on/off current ratio in a wide range of temperatures including high temperatures. This superb switch is an enabler of new memory devices and multiply-accumulate operation circuits used in AI.

Conventional floating-gate non-volatile memory writes data by injecting a charge into the gate insulating film of the transistor; however, the high energy necessary for the injection causes the insulating film to degrade, leading to limitation in write cycles. Conversely, memory devices using the OSFET can write data by switching the OSFET on and off, making this device an ideal memory device with no degradation in principle.

▲ Schematic diagram representing OSFET switching

>>> NOSRAM®, Memory using OSFET

High-Performance Device Achieved with Crystalline OS

High-performance displays and LSI devices which are difficult to manufacture with conventional techniques can be realized by using crystalline OS. SEL provides and develops such novel, high-performance devices.

1) FET・・・・・Field Effect Transistor
2) NOSRAM・・・・・Nonvolatile Oxide Semiconductor Random Access Memory
3) DOSRAM・・・・・Dynamic Oxide Semiconductor Random Access Memory

* CAAC, CAAC-OS, OSFET, NOSRAM, DOSRAM are registered trademarks of Semiconductor Energy Laboratory Co., Ltd.
(Japanese trademark registration No. 5473530, No. 5473535, No. 5519759, No. 6544563, and No. 6544564).