Group III-V semiconductor device with strain-relieving interlayers

A method for forming a group III-V semiconductor device over a substrate, said method comprising:

• forming at least one transition layer situated over said substrate;
• forming a first strain-relieving interlayer over said at least one transition layer and a second strain-relieving interlayer over said first strain-relieving interlayer;
• forming a first group III-V semiconductor body over said second strain-relieving interlayer, said first group III-V semiconductor body substantially thicker than said first and second strain-relieving interlayers;
• said first and second strain-relieving interlayers comprising different semiconductor materials so as to reduce a strain in said first group III-V semiconductor body;
• said first strain-relieving interlayer at least five times thicker than said second strain-relieving interlayer;
• said second strain-relieving interlayer being an aluminum nitride (AlN) layer.