Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device comprising:

• forming a semiconductor stack on a semiconductor substrate;
• forming an ohmic electrode including Al on the semiconductor stack;
• forming a SiN film covering the ohmic electrode;
• forming a first photoresist on the SiN film, the first photoresist having an opening pattern overlapping the ohmic electrode;
• performing a first heat treatment on the first photoresist at a first temperature;
• performing ultraviolet curing of the first photoresist;
• forming an opening in the SiN film so as to cause a surface of the ohmic electrode to be exposed inside the opening, the opening overlapping the opening pattern;
• forming a barrier metal layer on the first photoresist and on the ohmic electrode exposed through the opening;
• forming a second photoresist in the opening pattern;
• performing a second heat treatment on the second photoresist at a second temperature to cover a part of the barrier metal layer with the second photoresist, the part of the barrier metal layer overlapping the opening;
• and
• etching the barrier metal layer using the second photoresist,
• wherein the second temperature is higher than the first temperature.