Compound semiconductor device and method for manufacturing the same

1. A compound semiconductor device comprising:

a compound semiconductor laminated structure;

an electrode formed above the compound semiconductor laminated structure; and

a p-type semiconductor layer formed between the compound semiconductor laminated structure and the electrode,

wherein an underlying film that has a lower coefficient of thermal expansion than the p-type semiconductor layer is formed between the compound semiconductor laminated structure and the p-type semiconductor layer, and

wherein the p-type semiconductor layer has tensile strain in a direction parallel to a surface of the compound semiconductor laminated structure resulting from a difference in coefficient of thermal expansion from the underlying film.

2. The compound semiconductor device according to claim 1 , wherein

an opening is formed in the underlying film, and

the p-type semiconductor layer is formed on the underlying film so as to fill in the opening.

3. A method for manufacturing the compound semiconductor device comprising:

forming a compound semiconductor laminated structure; and

forming a p-type semiconductor layer in an electrode forming region above the compound semiconductor laminated structure,

forming an underlying film that has a lower coefficient of thermal expansion than the p-type semiconductor layer between the compound semiconductor laminated structure and the p-type semiconductor layer, wherein

the p-type semiconductor layer has tensile strain in a direction parallel to a surface of the compound semiconductor laminated structure resulting from a difference in coefficient of thermal expansion from the underlying film.

4. The method for manufacturing the compound semiconductor device according to claim 3 , wherein

an opening is formed in the underlying film, and

the p-type semiconductor layer is formed on the underlying film so as to fill in the opening.