Abstract: To realize an ohmic electrode having practically satisfactory characteristics relative to GaAs semiconductors, first formed on an n+-type GaAs substrate are a Ni thin film with a thickness between 8 nm and 30 nm, an In thin film with a thickness between 2 nm and 6 nm and a Ge thin film with a thickness between 10 nm and 50 nm, sequentially. After that, the n+-type GaAs substrate having formed the Ni thin film, In thin film and Ge thin film is annealed at a temperature between 300 to 600° C. for a few seconds to minutes. As a result, the ohmic electrode has a multi-layered structure including an n++-type re-grown GaAs layer re-grown from the n+-type GaAs substrate, InGaAs layer and NiGe thin film. Alternatively, before the annealing, a thin film of a refractory metal or its compound, such as Nb thin film, with or without another thin film of a wiring metal, such as Au thin film, may be further formed on the Ge thin film.