Patent ID: 7518154

Claim:
A substrate system for fabrication of a semiconductor element, comprising: (a) a substrate proper having a major surface; (b) a buffer region formed on the major surface of the substrate proper, the buffer region being a lamination of a plurality of buffer layers, each buffer layer comprising: (i) a first buffer sublayer of a first nitride semiconductor containing aluminum in a first proportion; (ii) a second buffer sublayer of a second nitride semiconductor containing aluminum in a second proportion which is either zero or less than the first proportion, the second buffer sublayer being arranged next to the first buffer sublayer and farther away from the substrate proper than is the first buffer sublayer; and (iii) a third buffer sublayer of a third nitride semiconductor containing aluminum in a third proportion which is intermediate the first and the second proportion, the third buffer sublayer being arranged next to the second buffer sublayer and farther away from the substrate proper than is the second buffer sublayer; and (c) a main semiconductor region for a desired semiconductor element formed on the major surface of the substrate proper via the buffer region, the main semiconductor region having at least one nitride semiconductor layer.