Semiconductor device, method for manufacturing the same, or display device including the same

A semiconductor device comprising:

• a transistor including:
• a first gate electrode;
• a first insulating film over the first gate electrode;
• an oxide semiconductor film over the first insulating film;
• a source electrode electrically connected to the oxide semiconductor film;
• a drain electrode electrically connected to the oxide semiconductor film;
• a second insulating film over the oxide semiconductor film;
• a second gate electrode over the second insulating film;
• and
• a third insulating film over the second gate electrode,
• wherein the second gate electrode is electrically connected to the first gate electrode through an opening portion in the first insulating film and the second insulating film,
• wherein the oxide semiconductor film includes a first oxide semiconductor film on the first gate electrode side, and a second oxide semiconductor film over the first oxide semiconductor film,
• wherein the first oxide semiconductor film and the second oxide semiconductor film include In, M, and Zn,
• wherein M is Al, Ga, Y, or Sn,
• wherein, in a region of the second oxide semiconductor film, the number of atoms of the In is smaller than that in the first oxide semiconductor film, and
• wherein the second gate electrode includes at least one metal element included in the oxide semiconductor film.

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

• forming a first gate electrode;
• forming a first insulating film over the first gate electrode;
• forming a first oxide semiconductor film over the first insulating film;
• forming a second oxide semiconductor film over the first oxide semiconductor film;
• forming a source electrode and a drain electrode over the second oxide semiconductor film;
• forming a second insulating film over the second oxide semiconductor film, the source electrode, and the drain electrode;
• forming a third oxide semiconductor film functioning as a second gate electrode, over the second insulating film;
• and
• forming a third insulating film including hydrogen, over the third oxide semiconductor film,
• wherein, in the step of forming the first oxide semiconductor film, the first oxide semiconductor film is formed in an atmosphere including a first oxygen gas, and the first oxygen gas is added to the first insulating film,
• wherein, in the step of forming the second oxide semiconductor film, the second oxide semiconductor film is formed in an atmosphere including a second oxygen gas,
• wherein, in the step of forming the third oxide semiconductor film, the third oxide semiconductor film is formed in an atmosphere including a third oxygen gas, and the third oxygen gas is added to the second insulating film, and
• wherein, in the step of forming the third insulating film or after the step of forming the third insulating film, the hydrogen is added from the third insulating film to the third oxide semiconductor film.

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

• forming a first gate electrode;
• forming a first insulating film over the first gate electrode;
• forming a first oxide semiconductor film over the first insulating film;
• forming a second oxide semiconductor film over the first oxide semiconductor film;
• forming a source electrode and a drain electrode over the second oxide semiconductor film;
• forming a second insulating film over the second oxide semiconductor film, the source electrode, and the drain electrode;
• forming a third oxide semiconductor film functioning as a second gate electrode, over the second insulating film;
• forming a fourth oxide semiconductor film functioning as the second gate electrode, over the third oxide semiconductor film;
• and
• forming a third insulating film including hydrogen, over the fourth oxide semiconductor film,
• wherein, in the step of forming the first oxide semiconductor film, the first oxide semiconductor film is formed in an atmosphere including a first oxygen gas, and the first oxygen gas is added to the first insulating film,
• wherein, in the step of forming the second oxide semiconductor film, the second oxide semiconductor film is formed in an atmosphere including a second oxygen gas,
• wherein, in the step of forming the third oxide semiconductor film, the third oxide semiconductor film is formed in an atmosphere including a third oxygen gas, and the third oxygen gas is added to the second insulating film,
• wherein, in the step of forming the fourth oxide semiconductor film, the fourth oxide semiconductor film is formed in an atmosphere including a fourth oxygen gas, and
• wherein, in the step of forming the third insulating film or after the step of forming the third insulating film, the hydrogen is added from the third insulating film to the fourth oxide semiconductor film.