Semiconductor device, display device, and semiconductor device manufacturing method

A semiconductor device comprising:

• a substrate;
• a gate electrode provided on the substrate;
• a gate insulating film formed on the gate electrode;
• an islanded oxide semiconductor layer formed on the gate insulating film and including a channel region and first and second contact regions that are arranged to interpose the channel region between them;
• a source electrode electrically connected to the first contact region;
• a drain electrode electrically connected to the second contact region;
• and
• a protective film formed on and in contact with the oxide semiconductor layer and arranged between the oxide semiconductor layer and the source and drain electrodes,
• wherein the upper and side surfaces of the oxide semiconductor layer are covered with the source electrode, the drain electrode and the protective film, and
• when viewed along a normal to the substrate, the narrowest gap between the respective outer peripheries of the first contact region and the source electrode and the narrowest gap between the respective outer peripheries of the second contact region and the drain electrode both have a length of 1.5 μm to 4.5 μm.

A method for fabricating a semiconductor device, the method comprising the steps of:

• (A) forming a gate electrode on a substrate;
• (B) forming a gate insulating film to cover the gate electrode;
• (C) forming an islanded oxide semiconductor layer on the gate insulating film;
• (D) forming a protective film with first and second holes on the oxide semiconductor layer;
• and
• (E) forming a source electrode and a drain electrode electrically connected to the oxide semiconductor layer through the first and second holes, respectively,
• wherein the steps (D) and (E) are performed so that the upper and side surfaces of the oxide semiconductor layer are covered with the source and drain electrodes and the protective film, and
• the step (E) is performed so that when viewed along a normal to the substrate, the narrowest gap between the respective outer peripheries of the first hole and the source electrode and the narrowest gap between the respective outer peripheries of the second hole and the drain electrode both have a length of 1.5 μm to 4.5 μm.