Patent ID: 8525225

Claim:
A semiconductor device comprising: a plurality of electrodes including a first electrode and a second electrode arranged on a nitride-based compound semiconductor layer grown on a substrate; and a surface protection film that covers a surface of a semiconductor layer on the compound semiconductor layer between the electrodes by extending in direct contact with all the surface of the semiconductor layer from the first electrode to the second electrode of the plurality of electrodes, wherein the surface protection film is a dielectric film of silicon nitride expressed by formula SiN x , and a value of x , which is a composition ratio of silicon and nitrogen, is determined to be in a range by which a refractive index of the surface protection film along all of the surface of the semiconductor layer from the first electrode to the second electrode is equal to or greater than 2.0 and equal to or less than 2.09 in order to minimize leakage current.