Field-effect transistor, method for producing same, display element, display device, and system

A field-effect transistor comprising:

• a semiconductor film formed on a base;
• a gate insulating film formed on a part of the semiconductor film;
• a gate electrode including a plurality of layers formed on the gate insulating film;
• and
• a source electrode and a drain electrode formed in contact with the semiconductor film, wherein
• widths of the plurality of layers become narrower layer by layer toward the gate insulating film,
• a thickness of the source electrode and the drain electrode is smaller than a total thickness of the gate insulating film and the gate electrode excluding an uppermost layer, and
• the gate insulating film includes a region that is not in contact with the source electrode or the drain electrode.

A method for producing a field-effect transistor, comprising:

• forming a semiconductor film on a base;
• forming a gate insulating film on a part of the semiconductor film;
• forming a gate electrode on the gate insulating film;
• patterning the gate electrode and the gate insulating film by etching using a same mask;
• and
• forming a source electrode and a drain electrode in contact with the semiconductor film, wherein,
• in the forming of the source electrode and the drain electrode, the source electrode and the drain electrode are formed such that a thickness of the source electrode and the drain electrode is smaller than a thickness of the gate insulating film, and the gate insulating film has a region that is not in contact with either the source electrode or the drain electrode.