Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• an oxide semiconductor stack;
• a gate electrode layer comprising a region overlapping with the oxide semiconductor stack;
• a gate insulating layer between the oxide semiconductor stack and the gate electrode layer;
• and
• a first electrode layer and a second electrode layer electrically connected to the oxide semiconductor stack;
• wherein the oxide semiconductor stack includes a first oxide semiconductor layer and a second oxide semiconductor layer comprising a crystalline structure over the first oxide semiconductor layer,
• wherein the first oxide semiconductor layer includes a layer expressed as InMXZnYOZ (X≧1, Y>1, Z>0, and M is one or more metal elements selected from Ga, Mg, Hf, Al, Sn, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu),
• wherein the second oxide semiconductor layer includes an indium zinc oxide layer, and
• wherein an amount of oxygen vacancies of the first oxide semiconductor layer in a top side of the first oxide semiconductor layer is lower than an amount of oxygen vacancies of the first oxide semiconductor layer in a bottom side of the first oxide semiconductor layer.

A semiconductor device comprising:

• a first gate electrode layer;
• a first gate insulating layer over the first gate electrode layer;
• a first oxide semiconductor layer over the first gate insulating layer;
• a second oxide semiconductor layer over the first oxide semiconductor layer;
• a first electrode layer on and in contact with the second oxide semiconductor layer;
• and
• a second electrode layer on and in contact with the second oxide semiconductor layer;
• wherein the first oxide semiconductor layer includes an indium zinc oxide layer,
• wherein the second oxide semiconductor layer includes a layer expressed as InMXZnYOZ (X≧1, Y>1, Z>0, and M is one or more metal elements selected from Ga, Mg, Hf, Al, Sn, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), and
• wherein an amount of oxygen vacancies of the second oxide semiconductor layer in a bottom side of the second oxide semiconductor layer is lower than an amount of oxygen vacancies of the second oxide semiconductor layer in a top side of the second oxide semiconductor layer.

A semiconductor device comprising:

• a first oxide semiconductor layer;
• a second oxide semiconductor layer over the first oxide semiconductor layer;
• a first electrode layer on and in contact with the second oxide semiconductor layer;
• a second electrode layer on and in contact with the second oxide semiconductor layer;
• a first gate insulating layer over the second oxide semiconductor layer, the first electrode layer, and the second electrode layer;
• and
• a first gate electrode layer over the first gate insulating layer;
• wherein the first oxide semiconductor layer includes an indium zinc oxide layer,
• wherein the second oxide semiconductor layer includes a layer expressed as InMXZnYOZ (X≧1, Y>1, Z>0, and M is one or more metal elements selected from Ga, Mg, Hf, Al, Sn, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), and
• wherein an amount of oxygen vacancies of the second oxide semiconductor layer in a bottom side of the second oxide semiconductor layer is lower than an amount of oxygen vacancies of the second oxide semiconductor layer in a top side of the second oxide semiconductor layer.