Semiconductor device including oxide semiconductor film

• US 9,324,810 B2
• Filed: 11/25/2013
• Issued: 04/26/2016
• Est. Priority Date: 11/30/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Tokunaga, Hajime, Koezuka, Junichi, Okazaki, Kenichi, Yamazaki, Shunpei
• Primary Examiner(s): Jackson Jr, Jerome
• Assistant Examiner(s): Peters, Charles R
• Application Number:
  US14/089,085
• Publication Number:
  US 20140151685A1
• Time in Patent Office: 883 Days
• Field of Search: 257/43, 257/40, 257/194, 257/414, 257/53, 257/66, 257/E39.016, 257/59, 257/72, 438/104, 438/3, 438/49, 438/105, 438/151, 438/481, 438/485, 438/85
• US Class Current: 1/1
• CPC Class Codes: H01L 29/22 including, apart from doping materials or other impurities, only AIIBVI compounds
• CPC Class Codes: H01L 29/247 Amorphous materials
• CPC Class Codes: H01L 29/78606 with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device H01L29/78642, H01L29/78645 take precedence
• CPC Class Codes: H01L 29/78648 arranged on opposing sides of the channel
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H01L 29/78693 the semiconducting oxide being amorphous
• CPC Class Codes: H01L 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621

Abstract

A highly reliable semiconductor device having stable electrical characteristics is provided. Oxide films each containing one or more kinds of metal elements included in an oxide semiconductor film are formed in contact with an upper side and a lower side of the oxide semiconductor film where a channel is formed, whereby interface states are not easily generated at an upper interface and a lower interface of the oxide semiconductor film. A material which has a lower electron affinity than the oxide semiconductor film is used for the oxide films in contact with the oxide semiconductor film, whereby electrons flowing in the channel hardly move in the oxide films and mainly move in the oxide semiconductor film. Thus, even when an interface state exists between the oxide film and an insulating film formed on the outside of the oxide film, the state hardly influences the movement of electrons.

Claims

1. A semiconductor device comprising:

a first electrode;

a first insulating film over the first electrode;

an oxide semiconductor film comprising gallium over the first insulating film;

a first oxide film over and in contact with the oxide semiconductor film;

a second electrode over the first oxide film;

a third electrode over the first oxide film; and

a second oxide film over and in contact with the first oxide film, the second electrode, and the third electrode, and

wherein each of the first oxide film and the second oxide film comprises indium, gallium, and zinc,

wherein electron affinity of the second oxide film is equal to or lower than electron affinity of the first oxide film, and

wherein the electron affinity of the second oxide film is lower than electron affinity of the oxide semiconductor film.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor film, the first oxide film, and the second oxide film each comprise same metal elements.

3. The semiconductor device according to claim 1, further comprising a second insulating film over and in contact with the second oxide film,

wherein the second insulating film contains excess oxygen.

4. The semiconductor device according to claim 3, wherein the second insulating film is a stack of an oxide insulating film and a nitride insulating film.

5. A semiconductor device comprising:

a first electrode;

a first insulating film over the first electrode;

a first oxide film over the first insulating film;

an oxide semiconductor film comprising gallium over the first oxide film;

a second oxide film over and in contact with the oxide semiconductor film;

a second electrode over the second oxide film;

a third electrode over the second oxide film; and

a third oxide film over and in contact with the second oxide film, the second electrode, and the third electrode,

wherein each of the first oxide film, the second oxide film, and the third oxide film comprises indium, gallium, and zinc.

6. The semiconductor device according to claim 5, wherein the oxide semiconductor film further comprises indium and zinc.

7. The semiconductor device according to claim 5, wherein the oxide semiconductor film, the first oxide film, the second oxide film, and the third oxide film each comprise same metal elements.

8. The semiconductor device according to claim 5,

wherein electron affinity of the third oxide film is the same as electron affinity of the first oxide film and electron affinity of the second oxide film, and

wherein the electron affinity of the third oxide film is lower than electron affinity of the oxide semiconductor film.

9. The semiconductor device according to claim 5,

wherein electron affinity of the third oxide film is lower than electron affinity of the first oxide film and electron affinity of the second oxide film, and

wherein the electron affinity of the first oxide film and the electron affinity of the second oxide film are lower than electron affinity of the oxide semiconductor film.

10. The semiconductor device according to claim 5,

wherein electron affinity of the third oxide film is the same as electron affinity of the second oxide film,

wherein the electron affinity of the third oxide film is higher than electron affinity of the first oxide film, and

wherein the electron affinity of the third oxide film is lower than electron affinity of the oxide semiconductor film.

11. The semiconductor device according to claim 5,

wherein electron affinity of the third oxide film is the same as electron affinity of the first oxide film,

wherein the electron affinity of the third oxide film is lower than electron affinity of the second oxide film, and

wherein the electron affinity of the third oxide film is lower than electron affinity of the oxide semiconductor film.

12. The semiconductor device according to claim 5, further comprising a second insulating film over and in contact with the third oxide film,

wherein the second insulating film contains excess oxygen.

13. The semiconductor device according to claim 12, wherein the second insulating film is a stack of an oxide insulating film and a nitride insulating film.