Semiconductor device having specified relative material concentration between In—Ga—Zn—O films

A display device comprising:

• a gate electrode over a substrate;
• a gate insulating film over the gate electrode;
• a first In—Ga—Zn oxide film over the gate insulating film;
• a second In—Ga—Zn oxide film over the first In—Ga—Zn oxide film;
• a pair of electrodes over the second In—Ga—Zn oxide film, the pair of electrodes comprising titanium;
• a first oxide insulating film over the pair of electrodes, the first oxide insulating film having a region being in contact with the second In—Ga—Zn oxide film;
• a pixel electrode over the first oxide insulating film, the pixel electrode electrically connected to one of the pair of electrodes;
• and
• a liquid crystal layer over the pixel electrode,
• wherein the first In—Ga—Zn oxide film comprises In, Ga, and Zn at an atomic ratio of 1:1:1, and
• wherein the second In—Ga—Zn oxide film comprises In, Ga, and Zn at an atomic ratio of 1:3:6.

A display device comprising:

• a gate electrode over a substrate;
• a gate insulating film over the gate electrode;
• a first In—Ga—Zn oxide film over the gate insulating film;
• a second In—Ga—Zn oxide film over and in contact with the first In—Ga—Zn oxide film;
• a pair of electrodes over and in contact with the second In—Ga—Zn oxide film, the pair of electrodes comprising titanium;
• a pixel electrode electrically connected to one of the pair of electrodes;
• and
• a liquid crystal layer over the pixel electrode,
• wherein the gate insulating film comprises a nitride insulating film and an oxide insulating film provided over the nitride insulating film,
• wherein the first In—Ga—Zn oxide film comprises In, Ga, and Zn at an atomic ratio of 1:1:1, and
• wherein the second In—Ga—Zn oxide film comprises In, Ga, and Zn at an atomic ratio of 1:3:6.