Metal oxide, field-effect transistor, and method for producing the same

A field-effect transistor comprising:

• a source electrode and a drain electrode;
• a gate electrode;
• an active layer;
• and
• a gate insulating layer,
• wherein the gate insulating layer is etched,
• the gate insulating layer is a metal oxide including A element and at least one selected from the group consisting of B element and C element,
• the A element is at least one selected from the group consisting of Sc, Y, Ln (lanthanoid), Sb, Bi, and Te,
• the B element is at least one selected from the group consisting of Ga, Ti, Zr, and Hf,
• the C element is at least one selected from the group consisting of Group 2 elements in a periodic table,
• at least one selected from the group consisting of the source electrode and the drain electrode, the gate electrode, and the active layer is formed using etching solution A, and
• the gate insulating layer is etched using etching solution B that is an etching solution having same type as the etching solution A.

A metal oxide that functions as a gate insulating layer of a field-effect transistor, the metal oxide comprising:

• A element;
• and
• at least one selected from the group consisting of B element and C element,
• wherein the A element is at least one selected from the group consisting of Sc, Y, Ln (lanthanoid), Sb, Bi, and Te,
• the B element is at least one selected from the group consisting of Ga, Ti, Zr, and Hf,
• the C element is at least one selected from the group consisting of Group 2 elements in a periodic table, and
• an etching rate of the metal oxide in a wet etching solution including nitric acid is 0.1 nm/s or more but 20 nm/s or less.