Semiconductor device and method for manufacturing the semiconductor device

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

• forming an oxide semiconductor film over an insulating surface;
• forming a hard mask over the oxide semiconductor film;
• forming an organic coating film over the hard mask;
• forming a resist over the organic coating film;
• performing light exposure to form a resist mask;
• processing the organic coating film and the hard mask using the resist mask to form a processed hard mask;
• processing the oxide semiconductor film using the processed hard mask;
• removing the resist mask, the organic coating film, and the processed hard mask;
• forming a source electrode and a drain electrode in contact with the oxide semiconductor film;
• forming a gate insulating film over the source electrode and the drain electrode;
• and
• forming a gate electrode over the gate insulating film, the gate electrode overlapping with the oxide semiconductor film.

A semiconductor device comprising:

• an oxide semiconductor film over an insulating surface;
• a source electrode and a drain electrode in contact with the oxide semiconductor film;
• a gate insulating film over the source electrode and the drain electrode;
• and
• a gate electrode over the gate insulating film, the gate electrode overlapping with the oxide semiconductor film,
• wherein a distance between the source electrode and the drain electrode is greater than or equal to 1 nm and less than or equal to 30 nm, and
• wherein a standard deviation of line edge roughness of the oxide semiconductor film is less than or equal to 4 nm.