SEMICONDUCTOR DEVICE AND DISPLAY DEVICE INCLUDING THE SEMICONDUCTOR DEVICE
To improve field-effect mobility and reliability of a transistor including an oxide semiconductor film. A semiconductor device includes an oxide semiconductor film, a gate electrode, an insulating film over the gate electrode, the oxide semiconductor film over the insulating film, and a pair of electrodes over the oxide semiconductor film. The oxide semiconductor film includes a first oxide semiconductor film and a second oxide semiconductor film over the first oxide semiconductor film. The first oxide semiconductor film and the second oxide semiconductor film, include the same element. The first oxide semiconductor film includes a region having lower crystallinity than the second oxide semiconductor film.
1 . A semiconductor device comprising:
a gate electrode;
an insulating film over the gate electrode;
an oxide semiconductor film over the insulating film; and
a pair of electrodes over the oxide semiconductor film,
wherein the oxide semiconductor film includes a first oxide semiconductor film and a second oxide semiconductor film over the first oxide semiconductor film,
wherein the first oxide semiconductor film and the second oxide semiconductor film each independently include In, M, and Zn,
wherein the M is Al, Ga, Y, or Sn,
wherein the first oxide semiconductor film includes a region having lower crystallinity than the second oxide semiconductor film,
wherein an atomic ratio of the M to a total sum of the In, the M, and the Zn is higher than or equal to 1.5 and lower than or equal to 2.5 when an atomic ratio of the In is 4, and
wherein an atomic ratio of the Zn to the total sum of the In, the M, and the Zn is higher than or equal to 2 and lower than or equal to 4 when the atomic ratio of the In is 4.
2 . The semiconductor device according to claim 1 ,
wherein the atomic ratio between the In, the M, and the Zn is In:M:Zn=4:2:3 or in its neighborhood.
3 . A semiconductor device according to claim 1 ,
wherein the second oxide semiconductor film includes a crystal part, and
wherein the crystal part has a c-axis alignment.
4 . A display device comprising:
the semiconductor device according to claim 1 ; and
a display element.
5 . An electronic device comprising:
the display device according to claim 4 ; and
an operation key or a battery.
6 . A semiconductor device comprising:
a gate electrode;
an insulating film over the gate electrode;
an oxide semiconductor film over the insulating film; and
a pair of electrodes over the oxide semiconductor film,
wherein the oxide semiconductor film includes a first oxide semiconductor film and a second oxide semiconductor film over the first oxide semiconductor film,
wherein the first oxide semiconductor film and the second oxide semiconductor film each independently include In, M, and Zn,
wherein the M is Al, Ga, Y, or Sn,
wherein the first oxide semiconductor film includes a region having lower crystallinity than the second oxide semiconductor film,
wherein an atomic ratio of the M to a total sum of the In, the M, and the Zn is higher than or equal to 0.5 and lower than or equal to 1.5 when an atomic ratio of the In is 5, and
wherein an atomic ratio of the Zn to the total sum of the In, the M, and the Zn is higher than or equal to 5 and lower than or equal to 7 when the atomic ratio of the In is 5.
7 . The semiconductor device according to claim 6 ,
wherein the atomic ratio between the In, the M, and the Zn is In:M:Zn=5:1:6 or in its neighborhood.
8 . A semiconductor device according to claim 6 ,
wherein the second oxide semiconductor film includes a crystal part, and
wherein the crystal part has a c-axis alignment.
9 . A display device comprising:
the semiconductor device according to claim 6 ; and
a display element.
10 . An electronic device comprising:
the display device according to claim 9 ; and
an operation key or a battery.
11 . A semiconductor device comprising:
a gate electrode;
an insulating film over the gate electrode;
an oxide semiconductor film over the insulating film; and
a pair of electrodes over the oxide semiconductor film,
wherein the oxide semiconductor film includes a first oxide semiconductor film 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 the same element,
wherein an electron affinity of the first oxide semiconductor film is larger than an electron affinity of the second oxide semiconductor film,
wherein a difference between the electron affinity of the first oxide semiconductor film and the electron affinity of the second oxide semiconductor film is more than or equal to 0.15 eV and less than or equal to 2.0 eV, and
wherein the first oxide semiconductor film includes a region having lower crystallinity than the second oxide semiconductor film.
12 . The semiconductor device according to claim 11 ,
wherein the first oxide semiconductor film and the second oxide semiconductor film each independently include In, M, and Zn, and
wherein the M is Al, Ga, Y, or Sn.
13 . A semiconductor device according to claim 11 ,
wherein the second oxide semiconductor film includes a crystal part, and
wherein the crystal part has a c-axis alignment.
14 . A display device comprising:
the semiconductor device according to claim 11 ; and
a display element.
15 . An electronic device comprising:
the display device according to claim 14 ; and
an operation key or a battery.
16 . A semiconductor device comprising:
a gate electrode;
an insulating film over the gate electrode;
an oxide semiconductor film over the insulating film; and
a pair of electrodes over the oxide semiconductor film,
wherein the oxide semiconductor film includes a first oxide semiconductor film and a second oxide semiconductor film over the first oxide semiconductor film,
wherein the first oxide semiconductor film and the second oxide semiconductor film each independently include In, M, and Zn,
wherein the M is Al, Ga, Y, or Sn,
wherein an atomic ratio of the In to the Zn in the first oxide semiconductor film is higher than an atomic ratio of the In to the Zn in the second oxide semiconductor film, and
wherein the first oxide semiconductor film includes a region having lower crystallinity than the second oxide semiconductor film.
17 . The semiconductor device according to claim 16 ,
wherein an atomic ratio of the M to a total sum of the In, the M, and the Zn in the first oxide semiconductor film is higher than or equal to 1.5 and lower than or equal to 2.5 when an atomic ratio of the In is 4,
wherein an atomic ratio of the Zn to the total sum of the In, the M, and the Zn in the first oxide semiconductor film is higher than or equal to 2 and lower than or equal to 4 when the atomic ratio of the In is 4,
wherein an atomic ratio of the M to a total sum of the In, the M, and the Zn in the second oxide semiconductor film is higher than or equal to 0.5 and lower than or equal to 1.5 when an atomic ratio of the In is 1, and
wherein an atomic ratio of the Zn to the total sum of the In, the M, and the Zn in the second oxide semiconductor film is higher than or equal to 0.1 and lower than or equal to 2 when the atomic ratio of the In is 1.
18 . The semiconductor device according to claim 17 ,
wherein the atomic ratio between the In, the M, and the Zn in the first oxide semiconductor film is In:M:Zn=4:2:3 or in its neighborhood, and
wherein the atomic ratio between the In, the M, and the Zn in the second oxide semiconductor film is In:M:Zn=1:1:1 or in its neighborhood.
19 . The semiconductor device according to claim 16 ,
wherein an atomic ratio of the M to a total sum of the In, the M, and the Zn in the first oxide semiconductor film is higher than or equal to 1.5 and lower than or equal to 2.5 when an atomic ratio of the In is 4,
wherein an atomic ratio of the Zn to the total sum of the In, the M, and the Zn in the first oxide semiconductor film is higher than or equal to 2 and lower than or equal to 4 when the atomic ratio of the In is 4,
wherein an atomic ratio of the M to a total sum of the In, the M, and the Zn in the second oxide semiconductor film is higher than or equal to 0.5 and lower than or equal to 1.5 when an atomic ratio of the In is 5, and
wherein an atomic ratio of the Zn to the total sum of the In, the M, and the Zn in the second oxide semiconductor film is higher than or equal to 5 and lower than or equal to 7 when the atomic ratio of the In is 5.
20 . The semiconductor device according to claim 19 ,
wherein the atomic ratio between the In, the M, and the Zn in the first oxide semiconductor film is In:M:Zn=4:2:3 or in its neighborhood, and
wherein the atomic ratio between the In, the M, and the Zn in the second oxide semiconductor film is In:M:Zn=5:1:6 or in its neighborhood.
21 . The semiconductor device according to claim 16 ,
wherein the first oxide semiconductor film includes a composite oxide semiconductor including a first region and a second region,
wherein the first region includes a plurality of first clusters,
wherein the plurality of first clusters includes one or both of the In and the Zn as its main component,
wherein the second region includes a plurality of second clusters,
wherein the plurality of second clusters includes one or more selected from the In, the M, and the Zn as its main component,
wherein the M is Al, Ga, Y, or Sn,
wherein the plurality of first clusters is connected to each other, and
wherein the plurality of second clusters is connected to each other.
22 . A semiconductor device according to claim 16 ,
wherein the second oxide semiconductor film includes a crystal part, and
wherein the crystal part has a c-axis alignment.
23 . A display device comprising:
the semiconductor device according to claim 16 ; and
a display element.
24 . An electronic device comprising:
the display device according to claim 23 ; and
an operation key or a battery.