The Future with Crystalline Oxide Semiconductors

Striving for Further Development of Electronics

We have focused on oxide semiconductors as a next-generation semiconductor material, and have pioneered research and development in this field.
From this work, we have found two new crystal structures for oxide semiconductors (OS): c-axis aligned crystalline oxide semiconductor (CAAC-OS®) and nanocrystalline oxide semiconductor (nc-OS®). We have also found first in the world that the FETs fabricated with these crystalline oxide semiconductor materials (CAAC-IGZO, in particular) exhibit unique characteristics.
In addition, we have discovered a distinctive material composition, which we term cloud-aligned composite (CAC), and increase the mobility of the FET (see S. Yamazaki et al., Jpn. J. Appl. Phys. 55, 115504, 2016).
One of the rare features of FETs fabricated with a crystalline oxide semiconductor material (OSFETs) is an extremely low off-state current that has yet to be measured by humankind. Using this feature, extremely low power consumption can be achieved.

Technical Information : CAAC-OS® Technology

The Hidden Potential of a Crystalline OS

Crystalline OS FETs have reached the world's lowest off-state current,
Ioff = 10-24A/㎛, at 85℃.

The most distinctive characteristic of an FET1) using crystalline oxide semiconductor (OS) is the extremely low off-state current on the order of yA/㎛ (10-24A/㎛), which cannot be achieved by a silicon semiconductor. Its physical property, a current ratio of more than 20 digits between the on-state and the off-state, can dramatically reduce the power consumption of devices.

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.

Technical Information : Memory devices using the OSFET : NOSRAM®

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.

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

*OSFET, CAAC, CAAC-OS, CAAC-IGZO, NOSRAM, and DOSRAM are registered trademarks of Semiconductor Energy Laboratory Co., Ltd.
(Japanese trademark registration No. 5519759, No. 5473530, No. 5473535, No. 5494218, No. 5529056, and No. 5519752).