A semiconductor power device of the present invention includes a first electrode and a second electrode, a breakdown voltage holding layer that is made of a semiconductor having a predetermined thickness and a predetermined impurity concentration, to which the first electrode and the second electrode are joined, and that has an active region in which carriers to generate electric conduction between the first electrode and the second electrode move, and an insulation film that is formed on the breakdown voltage holding layer and that has a high dielectric-constant portion having a higher dielectric constant than SiO2 at a part contiguous to the breakdown voltage holding layer.