Semiconductor power devices have conventionally become the focus of attention, which are mainly used for systems in various power electronics fields such as motor control systems and power conversion systems.
As semiconductor power devices of this type, SiC semiconductor devices having a trench-gate structure have been proposed, for example.
For example, Patent Literature 1 discloses a MIS transistor including an n+-type SiC substrate, an n−-type epitaxial layer (drift region) formed on the SiC substrate, an n+-type source region and a p-type body region formed in an active region of the epitaxial layer, a grid-shaped gate trench formed in a manner penetrating through the source region and the body region to reach the drift region, a gate insulating film formed on the inner surface of the gate trench, a gate electrode embedded in the gate trench, and a p-type guard ring formed in a transistor peripheral region formed in the active region.