Patent ID: 7632741

Claim:
A method for forming an AlGaN crystal layer, comprising the steps of: fabricating a template substrate by forming a first AlN layer on a specific single crystal base material; forming a second AlN layer at a temperature of 600° C. or lower in a Ga-containing atmosphere on said first AlN layer; and forming an AlGaN layer directly on said second AlN layer; wherein said first AlN layer is formed so as to have a flat surface at a substantially atomic level and so as to have an applied in-plane compressive stress in the step of forming said first AlN layer; wherein said second AlN layer is formed so as to have an applied in-plane compressive stress, that is relaxed compared with said in-plane compressive stress of said first AlN layer, in the step of forming said second AlN layer; and wherein said AlGaN layer is formed at a forming temperature of 1000° C. or higher in the step of forming said AlGaN layer.