This study reports on our cutting-edge packaging technology that achieves high power-cycling (PC) durability of silicon carbide (SiC) devices in high-temperature environments up to 250 °C. The key to improving durability is the precise adjustment of the coefficient of thermal expansion (CTE) of the buffer layer bonded onto the SiC chip. It suppresses the creep rupture of the aluminum chip electrode, resulting in a 2.7-fold improvement in the lifetime at 200 °C from the previously reported 334,000 to 905,000 cycles. The developed structure is subjected to a 250 °C test and a lifetime of 350,000 cycles is successfully demonstrated.