This paper describes the customized power MOSFET technologies that we have developed over the last twenty years for automotive use. During the 1980s we developed thermal-destruction free power MOSFETs with monolithically integrated polysilicon thermal sensing diodes (PTSDs), which are in wide use around the world. In the 1990s, we succeeded in developing the CONCAVE-DMOSFET, the first vertical channel power MOSFET for automotive use that achieves both lower dissipation and optimal gate reliability.
Recently, we have greatly advanced power MOSFET performance through the development of PTOx trench-gate MOSFETs (TMOSs), where PTOx stands for partially thick gate oxide film structure. The PTOx structure consists of thick oxide around the trench top, thin oxide on the trench sides, and thick oxide at the trench bottom, and is formed using a simple process that we developed. Estimated figures of merit (Ron*Qgd) compared with conventional devices are remarkably reduced by 32% at 60 V, 28% at 100 V, and 25% at 250 V. Fabricated PTOx-TMOSs of 100 V and 250 V denote high performance corresponding with the estimations, and stress reduction in the gate oxides against high electrical field has been successfully achieved, promising high reliability.