Semiconductor device

• US 10,714,626 B2
• Filed: 12/07/2017
• Issued: 07/14/2020
• Est. Priority Date: 04/02/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Pham, Thanhha S
• Application Number:
  US15/834,131
• Publication Number:
  US 20180166579A1
• Time in Patent Office: 950 Days
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 27/1251 comprising TFTs having a different architecture, e.g. top- and bottom gate TFTs
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/7831 with multiple gate structure FinFETs or MuGFETs H01L29/7855, thin film transistors H01L29/78645
• CPC Class Codes: H01L 29/786 Thin film transistors, i.e. transistors with a channel being at least partly a thin film transistors having only the source or the drain region on an insulator layer H01L29/0653; thin film FinFETs H01L29/785
• 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: H10K 10/46 Field-effect transistors, e.g. organic thin-film transistors [OTFT] H10K10/43 takes precedence
• CPC Class Codes: H10K 10/468 characterised by the gate dielectrics
• CPC Class Codes: H10K 10/474 the gate dielectric comprising a multilayered structure

Abstract

The oxide semiconductor film has the top and bottom surface portions each provided with a metal oxide film containing a constituent similar to that of the oxide semiconductor film. An insulating film containing a different constituent from the metal oxide film and the oxide semiconductor film is further formed in contact with a surface of the metal oxide film, which is opposite to the surface in contact with the oxide semiconductor film. The oxide semiconductor film used for the active layer of the transistor is an oxide semiconductor film highly purified to be electrically i-type (intrinsic) by removing impurities such as hydrogen, moisture, a hydroxyl group, and hydride from the oxide semiconductor and supplying oxygen which is a major constituent of the oxide semiconductor and is simultaneously reduced in a step of removing impurities.

Claims

1. A semiconductor device comprising:

a first gate electrode;

a first gate insulating film over the first gate electrode;

a first metal oxide film over and in contact with the first gate insulating film;

an oxide semiconductor film over and in contact with the first metal oxide film;

a source electrode and a drain electrode in contact with the oxide semiconductor film;

a second gate insulating film over the source electrode and the drain electrode; and

a second gate electrode over the second gate insulating film,

wherein the first metal oxide film comprises one or more constituent metal elements of the oxide semiconductor film, and

wherein a side surface of each of the first metal oxide film and the oxide semiconductor film is tapered and in contact with the source electrode or the drain electrode.

2. The semiconductor device according to claim 1, wherein at least part of a top surface of the oxide semiconductor film is in contact with the source electrode and the drain electrode.

3. The semiconductor device according to claim 1, wherein the first metal oxide film has a larger energy gap than the oxide semiconductor film.

4. The semiconductor device according to claim 1, wherein an energy at a bottom of a conduction band of the first metal oxide film is higher than an energy at a bottom of a conduction band of the oxide semiconductor film.

5. The semiconductor device according to claim 1, wherein the oxide semiconductor film comprises In, Ga, and Zn.

6. The semiconductor device according to claim 1, wherein the first metal oxide film comprises gallium.

7. A semiconductor device comprising:

a first gate electrode;

a first gate insulating film over the first gate electrode;

a first metal oxide film over and in contact with the first gate insulating film;

an oxide semiconductor film over and in contact with the first metal oxide film;

a source electrode and a drain electrode in contact with the oxide semiconductor film;

a second metal oxide film over the source electrode and the drain electrode;

a second gate insulating film over the second metal oxide film; and

a second gate electrode over the second gate insulating film,

wherein the first metal oxide film comprises one or more constituent metal elements of the oxide semiconductor film, and

wherein a side surface of each of the first metal oxide film and the oxide semiconductor film is tapered and in contact with the source electrode or the drain electrode.

8. The semiconductor device according to claim 7, wherein at least part of a top surface of the oxide semiconductor film is in contact with the source electrode and the drain electrode.

9. The semiconductor device according to claim 7, wherein the first metal oxide film has a larger energy gap than the oxide semiconductor film.

10. The semiconductor device according to claim 7, wherein an energy at a bottom of a conduction band of the first metal oxide film is higher than an energy at a bottom of a conduction band of the oxide semiconductor film.

11. The semiconductor device according to claim 7, wherein the oxide semiconductor film comprises In, Ga, and Zn.

12. The semiconductor device according to claim 7, wherein the first metal oxide film comprises gallium.