| 摘要 |
PROBLEM TO BE SOLVED: To suppress a change in threshold values caused by metal elements diffused from a gate electrode into a semiconductor layer and a channel layer in a compound semiconductor three-terminal device. SOLUTION: On an electron supply layer 23, a cap layer 24 including an opening 24A so formed as to correspond to the gate electrode 25 is formed. Then, a metal oxide film 29 formed of TiO2 or the like in such a thickness as to allow tunneling of carriers is so formed as to cover the cap layer 24. The metal oxide film 29 serves as a thin film for insulation and preventing the diffusion of the metal elements from the gate electrode. On the metal oxide film 29, a Pt layer 25B, 26B and 27B for suppressing the diffusion of Au atoms from the gate electrode 25C and ohmic electrodes 26C, 27C and a Ti layer 25A, 26A and 27A for securing the adhesion with the metal oxide film 29 are formed in layers in the order of the Ti layer, Pt layer, and Au electrodes.
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