Semiconductor device

• US 8,884,282 B2
• Filed: 03/29/2011
• Issued: 11/11/2014
• 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): Payen, Marvin
• Application Number:
  US13/074,623
• Publication Number:
  US 20110240992A1
• Time in Patent Office: 1,323 Days
• Field of Search: 257/43, 257/57, 257/E29.273
• US Class Current: 257/43
• 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 29/517 the insulating material comprising a metallic compound, e.g. metal oxide, metal silicate H01L29/518 takes precedence
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

A transistor is provided in which the bottom surface portion of an oxide semiconductor film is provided with a metal oxide film containing a constituent similar to that of the oxide semiconductor film, and an insulating film containing a different constituent from the metal oxide film and the oxide semiconductor film is formed in contact with a surface of the metal oxide film, which is opposite to the surface in contact with the oxide semiconductor film. In addition, 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) through heat treatment in which impurities such as hydrogen, moisture, hydroxyl, and hydride are removed from the oxide semiconductor and oxygen which is one of main component materials of the oxide semiconductor is supplied and is also reduced in a step of removing impurities.

Claims

1. A semiconductor device comprising:

a first insulating film;

a metal oxide film in contact with the first insulating film;

an oxide semiconductor film in contact with the metal oxide film;

a source electrode and a drain electrode in contact with the oxide semiconductor film and over the metal oxide film with the oxide semiconductor film interposed therebetween;

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

a gate electrode over the gate insulating film.

2. The semiconductor device, according to claim 1, wherein an energy gap of the metal oxide film is larger than an energy gap of the oxide semiconductor film.

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

4. The semiconductor device, according to claim 1, wherein the metal oxide film includes gallium oxide.

5. The semiconductor device, according to claim 1, wherein the first insulating film includes silicon oxide.

6. The semiconductor device, according to claim 1, wherein the gate insulating film includes silicon oxide or hafnium oxide.

7. The semiconductor device, according to claim 1, wherein side edges of the oxide semiconductor film in a channel length direction align with side edges of the metal oxide film in a channel length direction.

8. A semiconductor device comprising:

a first insulating film;

a metal oxide film in contact with the first insulating film;

an oxide semiconductor film in contact with the metal oxide film;

a source electrode and a drain electrode in contact with the oxide semiconductor film and over the metal oxide film with the oxide semiconductor film interposed therebetween;

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

a gate electrode over the gate insulating film,

wherein the metal oxide film includes oxide of one or a plurality of metal elements selected from constituent elements of the oxide semiconductor film.

9. The semiconductor device, according to claim 8, wherein an energy gap of the metal oxide film is larger than an energy gap of the oxide semiconductor film.

10. The semiconductor device, according to claim 8, wherein energy at a bottom of a conduction band of the metal oxide film is higher than energy at a bottom of a conduction band of the oxide semiconductor film.

11. The semiconductor device, according to claim 8, wherein the metal oxide film includes gallium oxide.

12. The semiconductor device, according to claim 8, wherein the first insulating film includes silicon oxide.

13. The semiconductor device, according to claim 8, wherein the gate insulating film includes silicon oxide or hafnium oxide.

14. The semiconductor device, according to claim 8, wherein side edges of the oxide semiconductor film in a channel length direction align with side edges of the metal oxide film in a channel length direction.