Patent ID: 9305773
Filing Date: 2016-04-05
CPC Classification: H01L

Claim Text:
1. A method for forming a nitride semiconductor layer, the method comprising forming a nitride semiconductor layer including a first stacked multilayer structure on a major surface of a substrate, the first stacked multilayer structure including: a first lower layer of a nitride semiconductor; a first intermediate layer of a nitride semiconductor; and a first upper layer of a nitride semiconductor, the first lower layer containing Si with a first concentration and having a first thickness, the first intermediate layer being provided on the first lower layer to be in contact with the first lower layer, containing Si with a second concentration lower than the first concentration, and having a second thickness thicker than the first thickness, the first upper layer being provided on the first intermediate layer to be in contact with the first intermediate layer, containing Si with a third concentration lower than the second concentration, and having a third thickness, the forming the nitride semiconductor layer including: forming the first lower layer with a first V/III ratio and at a first temperature; forming at least a part of the first intermediate layer on the first lower layer to be in contact with the first lower layer with a second V/III ratio lower than the first V/III ratio and at a second temperature not less than the first temperature; and forming the first upper layer on the first intermediate layer to be in contact with the first intermediate layer with a third V/III ratio lower than the first V/III ratio and higher than the second V/III ratio and at a third temperature higher than the second temperature.