Semiconductor power device and method for producing same

A semiconductor power device comprising:

• a first electrode and a second electrode;
• a breakdown voltage holding layer, the breakdown voltage holding layer being made of a semiconductor having a predetermined thickness and a predetermined impurity concentration, the first electrode and the second electrode being joined to the breakdown voltage holding layer, the breakdown voltage holding layer having an active region in which carriers to generate electric conduction between the first electrode and the second electrode move;
• and
• an insulation film, the insulation film being formed on the breakdown voltage holding layer, the insulation film having a high dielectric-constant portion having a higher dielectric constant than SiO2 at a part contiguous to the breakdown voltage holding layer, wherein
• in the active region, the breakdown voltage holding layer has a field-effect transistor structure including a first conductivity type source region, a second conductivity type body region contiguous to the source region, and a first conductivity type drift region contiguous to the body region,
• the first electrode includes a source electrode electrically connected to the source region,
• the second electrode includes a drain electrode electrically connected to the drift region,
• the high dielectric-constant portion is formed to be contiguous to the drift region
• the field-effect transistor structure has a trench gate structure including a gate trench formed in such a way as to straddle the source region, the body region, and the drift region,
• a gate electrode facing the body region is formed in the gate trench, and
• the insulation film includes a gate insulation film interposed between the gate electrode and an inner surface of the gate trench, and has the high dielectric-constant portion at a part contiguous to a bottom surface of the gate trench and/or a corner portion of the gate trench in the gate insulation film.