PURPOSE:To reduce a leakage current by covering the surface of a cathode with organic resist and oxidizing plasma in high frequency, thereby preventing the reverse sputtering from the cathode and reducing the irregular current density of the junction. CONSTITUTION:A lower electrode 2 is formed on a substrate 1, mounted on a cathode 5, a lower electrode surface is sputtered and cleaned in a high frequency plasma oxidizing vacuum tank 6, an oxidized film 3 to become a tunnel barrier is formed by a high frequency plasma oxidizing method by the cathode 5 covered with an AZ1470 on the surface, and the upper electrode 4 is deposited in the same tank 6. As the resist covered on the cathode the same resist as the mask can be used as part of the lower electrode in case of forming the oxidized film for the lower electrode.
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