Patent ID: 7973335
Filing Date: 2011-07-05
Classification: H01L

Abstract:
1. A field-effect transistor comprising a Group III nitride semiconductor layer structure including a heterojunction formed by a channel layer made of In x Ga 1-x N (0≦x≦1) and an electron supply layer made of Al y Ga 1-y N (0<y≦1), a source electrode and a drain electrode formed on the semiconductor layer structure while being separated from each other, a gate electrode arranged between said source electrode and said drain electrode, and an insulating film formed on said Group III nitride semiconductor layer, wherein said gate electrode has a field plate portion formed on said insulating film while said field plate portion has a visored shape that overhangs a gate side of said insulating film between said gate electrode and said drain electrode, and said insulating film has a multilayered film including a first insulating film and a second insulating film, said first insulating film being made of a compound that includes silicon and nitrogen as constituent elements, said second insulating film having a dielectric constant lower than that of said first insulating film, wherein said second insulating film is laminated on said first insulating film, and wherein said insulating film is formed having a double-stepped structure with first, second and third parallel regions in which the first parallel region is in contact with and disposed below the second parallel region, and in which the second parallel region is in contact with and disposed below the third parallel region.