Semiconductor device

A method for manufacturing a semiconductor device, comprising:

• forming a first conductivity-type drain layer:
• forming a first conductivity-type drift layer on the drain layer;
• forming a plurality of trenches in the drift layer;
• forming a first insulation film in a bottom portion of the trenches;
• forming a field plate electrode in each of the trenches above the first insulation film such that a space is maintained between the field plate electrode and sidewalls of the trench;
• filling the space within each trench with a second insulation film;
• forming a third insulation film on sidewalls of the trenches and above the second insulation film and each field plate electrode;
• and
• forming a gate electrode to be surrounded by the third insulation film in each of the trenches,
• wherein the second insulation film has a higher dielectric constant than the third insulation film.

A method for manufacturing a semiconductor device, comprising:

• forming a first conductivity-type drain layer:
• forming a first conductivity-type drift layer on the drain layer;
• forming a plurality of trenches in the drift layer;
• forming a first insulation film in a bottom portion of the trenches;
• forming a field plate electrode in each of the trenches above the first insulation film;
• forming a second insulation film on sidewalls of the trenches and on side surfaces of each field plate electrode such that a space is maintained between the second insulation film on the sidewalls of the trenches and the second insulation film on the side surfaces of each field plate electrode;
• filling the space between the second insulation film on the sidewalls of the trenches and the second insulation film on the side surfaces of each field plate electrode with a third insulation film;
• and
• forming a gate electrode in each of the trenches above the respective field plate electrode,
• wherein the third insulation film has a higher dielectric constant than the first and second insulation films.