Semiconductor device with field plate electrode

A semiconductor device comprising:

• a first electrode;
• a first semiconductor layer of first conductivity type provided on the first electrode;
• a first semiconductor region of second conductivity type provided on the first semiconductor layer;
• a second semiconductor region of first conductivity type provided on the first semiconductor region;
• a first insulating film provided in a trench reaching the first semiconductor layer from above the second semiconductor region via the second semiconductor region and the first semiconductor region, the first insulating film containing a first insulating material;
• a second electrode provided in the trench, the second electrode facing the first semiconductor layer via the first insulating film;
• a second insulating film provided between the second electrode and a fifth insulating film provided between the second electrode and the first semiconductor layer, the fifth insulating film containing the first insulating material, the second insulating film containing a second insulating material having a higher dielectric constant than the first insulating material;
• a third electrode provided above the second electrode and the first insulating film, the third electrode facing the first semiconductor region via a gate insulating film;
• an interlayer insulating film provided on the third electrode;
• a fourth electrode provided above the interlayer insulating film;
• and
• a fourth insulating film provided between the second electrode and the third electrode, wherein
• the second insulating film is not provided at least at a part of the bottom of the trench, and wherein
• the second insulating film includes a first insulating portion and a second insulating portion, and wherein
• the fourth insulating film is provided between the first insulating portion and the second insulating portion.