Semiconductor device and method for manufacturing same

A semiconductor device, comprising:

• a substrate;
• a gate electrode provided on the substrate;
• a first insulating layer formed on the gate electrode;
• an island-shaped oxide semiconductor layer formed on the first insulating layer;
• a source electrode electrically connected to the oxide semiconductor layer;
• a drain electrode electrically connected to the oxide semiconductor layer;
• and
• a protective layer covering an upper face of the oxide semiconductor layer,
• wherein at least one of the source electrode and the drain electrode is disposed on a portion of side faces of the oxide semiconductor layer and on a portion of side faces of the protective layer, and does not cover an upper face of the protective layer, and
• wherein the side faces of the oxide semiconductor layer include a first side face that has a first taper angle and a second side face that has a second taper angle that is smaller than the first taper angle, and said at least one of the source electrode and the drain electrode is formed on said first side face of the oxide semiconductor layer but is not formed on said second side face, said first taper angle being greater than or equal to 70 degrees and less than 90 degrees and said second taper angle being greater than or equal to 45 degrees and less than 70 degrees.