Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, comprising:

• forming a semiconductor layer above a substrate;
• forming a source electrode and a drain electrode on the semiconductor layer;
• forming a first insulating film covering a surface of the semiconductor layer, between the source electrode and the drain electrode;
• forming a second insulating film on the first insulating film;
• forming a mask on the second insulating film, the mask having an opening between the source electrode and the drain electrode in a plan view viewed in a direction perpendicular to an upper surface of the substrate;
• forming a first gate opening in the first insulating film and forming a second gate opening in the second insulating film, by etching the first insulating film and the second insulating film through the opening;
• and
• forming a gate electrode on the first insulating film and the second insulating film, the gate electrode making a Schottky contact with the semiconductor layer through the first gate opening and the second gate opening, wherein
• the opening includes
• a first side surface, and
• a second side surface closer to the drain electrode than the first side surface is to the drain electrode,
• an angle formed between the first side surface and the upper surface is larger than an angle formed between the second side surface and the upper surface,
• an etching rate of the second insulating film is higher than an etching rate of the first insulating film during the etching of the forming the first gate opening,
• an angle between the first side surface and the upper surface is in a range greater than or equal to 85° and less than or equal to 90°, and
• an angle between the second side surface and the upper surface is in a range greater than or equal to 45° and less than or equal to 60°.

A method for manufacturing a semiconductor device, comprising:

• forming a semiconductor layer above a substrate;
• forming a source electrode and a drain electrode on the semiconductor layer;
• forming a first insulating film covering a surface of the semiconductor layer, between the source electrode and the drain electrode:
• forming a second insulating film on the first insulating film:
• forming a mask on the second insulating film, the mask having an opening between the source electrode and the drain electrode in a plan view viewed in a direction perpendicular to an upper surface of the substrate:
• forming a first gate opening in the first insulating film and forming a second gate opening in the second insulating film, by etching the first insulating film and the second insulating film through the opening;
• and
• forming a gate electrode on the first insulating film and the second insulating film, the gate electrode making a Schottky contact with the semiconductor layer through the first gate opening and the second gate opening, wherein:
• the opening includes
• a first side surface, and
• a second side surface closer to the drain electrode than the first side surface is to the drain electrode,
• an angle formed between the first side surface and the upper surface is larger than an angle formed between the second side surface and the upper surface,
• an etching rate of the second insulating film is higher than an etching rate of the first insulating film during the etching of the forming the first gate opening, and
• an etching rate of the second insulating film is four times or more higher than an etching rate of the first insulating film during the etching of the forming the first gate opening.