The researcher has developed a high-reliability transistor with a unique structure in which built-in diodes does not suffer from current degradation, and verified its performance using a mass-production-quality prototype.

Ordinary transistor structure with a built-in SBD (left) and developed transistor structure

When voltage is applied to a built-in PiN diode that is structurally integrated into a transistor, the current gradually decreases. To address this problem, a transistor structure with a built-in SBD has been developed for a 3300-V-class transistor. However, the method cannot be applied to a 1200-V-class transistor. There was a need for a transistor with a built-in SBD for this class of withstand voltage.

The developed transistor has trench type gates and SBD built on a trench sidewall. The cell pitch, i.e., the spacing of the gates, was reduced to 5 µm, less than one third of the conventional pitch. Thus, the voltage applied to the PiN diodes was reduced and a high-reliability transistor that does not suffer from current degradation was developed.

With commercialization of this technology in mind, the researcher will enhance collaboration with companies and develop a multilayered device structure and an advanced production process. He will also develop peripheral technologies, such as a packaging technology.