Semiconductor device

• US 8,470,649 B2
• Filed: 12/01/2010
• Issued: 06/25/2013
• Est. Priority Date: 12/04/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei, Tsuji, Takahiro, Kusunoki, Koji, Miyairi, Hidekazu, Ochiai, Teruaki
• Primary Examiner(s): Pham, Hoai V
• Application Number:
  US12/957,429
• Publication Number:
  US 20110133196A1
• Time in Patent Office: 937 Days
• Field of Search: 438/48, 438/128, 438/149, 438/151, 438/157, 257/E21.617, 257/E21.053
• US Class Current: 438/149
• CPC Class Codes: H01L 29/45 Ohmic electrodes
• 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

An object is to provide a highly reliable transistor and a semiconductor device including the transistor. A semiconductor device including a gate electrode; a gate insulating film over the gate electrode; an oxide semiconductor film over the gate insulating film; and a source electrode and a drain electrode over the oxide semiconductor film, in which activation energy of the oxide semiconductor film obtained from temperature dependence of a current (on-state current) flowing between the source electrode and the drain electrode when a voltage greater than or equal to a threshold voltage is applied to the gate electrode is greater than or equal to 0 meV and less than or equal to 25 meV, is provided.

Claims

1. A method for manufacturing a semiconductor device, comprising the steps of:

performing a first heat treatment to a substrate;

forming a gate electrode over the substrate after performing the first heat treatment;

forming a gate insulating film over the gate electrode;

forming an oxide semiconductor layer over the gate insulating film;

forming a source electrode and a drain electrode so as to be electrically connected to the oxide semiconductor layer;

forming an insulating film over the oxide semiconductor layer; and

performing a second heat treatment after forming the oxide semiconductor layer.

2. The method according to claim 1, wherein the second heat treatment is performed for eliminating moisture and/or hydrogen in the oxide semiconductor layer.

3. The method according to claim 1, wherein the second heat treatment is performed before forming the insulating film.

4. The method according to claim 1, further comprising the step of performing a third heat treatment after forming the insulating film.

5. The method according to claim 4, wherein the third heat treatment is performed for repairing an oxygen-deficient portion in the oxide semiconductor layer.

6. The method according to claim 1, wherein the source electrode and the drain electrode are located below the insulating film.

7. A method for manufacturing a semiconductor device, comprising the steps of:

performing a first heat treatment to a substrate;

forming a gate electrode over the substrate;

forming a gate insulating film over the gate electrode;

forming an oxide semiconductor layer over the gate insulating film;

forming a conductive layer over the oxide semiconductor layer;

etching the conductive layer to form a source electrode and a drain electrode;

forming an insulating film over the oxide semiconductor layer; and

performing a second heat treatment after forming the oxide semiconductor layer.

8. The method according to claim 7, wherein the second heat treatment is performed for eliminating moisture and/or hydrogen in the oxide semiconductor layer.

9. The method according to claim 7, wherein the second heat treatment is performed before forming the insulating film.

10. The method according to claim 7, further comprising the step of performing a third heat treatment after forming the insulating film.

11. The method according to claim 10, wherein the third heat treatment is performed for repairing an oxygen-deficient portion in the oxide semiconductor layer.

12. The method according to claim 10, wherein the oxide semiconductor layer is etched to form a recessed portion in the oxide semiconductor layer during the etching step.

13. The method according to claim 10, wherein the gate electrode is formed after performing the first heat treatment.

14. The method according to claim 7, wherein the oxide semiconductor layer is etched to form a recessed portion in the oxide semiconductor layer during the etching step.

15. The method according to claim 7, wherein the gate electrode is formed after performing the first heat treatment.

16. A method for manufacturing a semiconductor device, comprising the steps of:

performing a first heat treatment to a substrate;

forming a gate electrode over the substrate;

forming a gate insulating film over the gate electrode;

forming an oxide semiconductor layer over the gate insulating film;

forming a first conductive layer over the oxide semiconductor layer;

etching the first conductive layer to form a source electrode and a drain electrode;

forming an insulating film over the oxide semiconductor layer;

performing a second heat treatment after forming the oxide semiconductor layer; and

forming a second conductive layer over the insulating film.

17. The method according to claim 16, wherein the second heat treatment is performed for eliminating moisture and/or hydrogen in the oxide semiconductor layer.

18. The method according to claim 16, wherein the second heat treatment is performed before forming the insulating film.

19. The method according to claim 16, further comprising the step of performing a third heat treatment after forming the insulating film.

20. The method according to claim 19, wherein the third heat treatment is performed for repairing an oxygen-deficient portion in the oxide semiconductor layer.