GaN device with N2 pre-treatment and method of performing N2 pre-treatment

A method of performing N2 pre-treatment to GaN device, comprising:

• providing a GaN device, comprising a GaN substrate, an AlGaN layer covering said GaN substrate, a p-GaN gate on said AlGaN layer and a TiN electrode on said p-GaN gate;
• forming a conformal first dielectric layer on said AlGaN layer, said p-GaN gate and said TiN electrode;
• forming a photoresist on said first dielectric layer, and said photoresist is provided with an opening completely overlapping said p-GaN gate in a direction vertical to said GaN substrate, wherein a horizontal spacing is between a sidewall of said opening and said p-GaN gate;
• performing an etching process to remove said first dielectric layer exposed from said photoresist;
• removing said photoresist;
• and
• using remaining said first dielectric layer as a mask to perform a N2 pre-treatment to an interface between said AlGaN layer and said GaN substrate not covered by said first dielectric layer.