Method for manufacturing semiconductor device

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

• forming a first electrode layer;
• stacking a first oxide film containing indium, gallium, zinc, and nitrogen as main components, an oxide semiconductor film containing indium, gallium, and zinc as main components, and a second oxide film containing indium, gallium, zinc, and nitrogen as main components in this order;
• forming a column object of the oxide semiconductor film and the second oxide film by etching the oxide semiconductor film in an etching step using a mixed solution of acetic acid, nitric acid, and phosphoric acid using the second oxide film as a mask while being receded in a line width direction, the column object standing over the first oxide film;
• forming a gate insulating film covering at least a side of the oxide semiconductor film of the column object and a first gate electrode layer and a second gate electrode layer which overlap with the oxide semiconductor film of the column object with the gate insulating film provided between the oxide semiconductor film and the first gate electrode layer and between the oxide semiconductor film and the second gate electrode layer and facing each other by stacking an insulating film and an island-shaped conductive film over the column object and anisotropically etching the insulating film and the island-shaped conductive film;
• and
• forming a second electrode layer electrically connected to the second oxide film of the column object.

A semiconductor device comprising:

• a first electrode layer;
• a first oxide film over the first electrode layer;
• an oxide semiconductor film over the first oxide film;
• a second oxide film over the oxide semiconductor film;
• a gate insulating film and a gate electrode layer covering a side surface of the oxide semiconductor film wherein the gate insulating film is between the oxide semiconductor film and the gate electrode layer;
• and
• a second electrode layer over the second oxide film.
• wherein the first oxide film contains indium, gallium, zinc, and nitrogen as main components,
• wherein the oxide semiconductor film contains indium, gallium, and zinc as main components, and
• wherein the second oxide film contains indium, gallium, zinc, and nitrogen as main components.