A solid-state snubber by a silicon carbide (SiC) p-n junction diode has been developed to suppress disturbing effect of surge voltage during turn-off transient of semiconductor devices. The operational performance was evaluated experimentally in a step-down DC/DC converter. As a result, it was found that a wiring inductance between the switching element (metal oxide semiconductor field effect transistor, MOSFET) and the solid-state snubber limits the surge-suppression performance. A co-pack, in which the MOSFET and the snubber are implemented on a same substrate contiguously, was developed to mitigates the effect by the parasitic inductance. The drastic enhancement in the surge-suppression performance with the co-pack configuration was obtained.