Semiconductor device comprising an oxide semiconductor

• US 8,766,252 B2
• Filed: 06/23/2011
• Issued: 07/01/2014
• Est. Priority Date: 07/02/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): VU, HUNG K
• Application Number:
  US13/167,049
• Publication Number:
  US 20120001169A1
• Time in Patent Office: 1,104 Days
• Field of Search: 257/43, 257/57, 257 66- 68, 257/71, 257/E21.412, 257/E29.289
• US Class Current: 257/43
• CPC Class Codes: H01L 21/02488 Insulating materials
• CPC Class Codes: H01L 21/02554 Oxides
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• 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 29/1037 and non-planar channel resulting from the gate electrode disposition, e.g. within a trench, H01L29/42356
• CPC Class Codes: H01L 29/2206 Amorphous materials
• CPC Class Codes: H01L 29/24 including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22 including organic materials H10K99/00
• CPC Class Codes: H01L 29/247 Amorphous materials
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/45 Ohmic electrodes
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/78618 characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure silicide contacts, electrodes in general H01L29/458
• 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

Abstract

A semiconductor device having favorable electric characteristics and a manufacturing method thereof are provided. A transistor includes an oxide semiconductor layer formed over an insulating layer, a source electrode layer and a drain electrode layer which overlap with part of the oxide semiconductor layer, a gate insulating layer in contact with part of the oxide semiconductor layer, and a gate electrode layer over the gate insulating layer. In the transistor, a buffer layer having n-type conductivity is formed between the source electrode layer and the oxide semiconductor layer and between the drain electrode layer and the oxide semiconductor layer. Thus, parasitic resistance is reduced, resulting in improvement of on-state characteristics of the transistor.

Claims

1. A semiconductor device comprising:

an oxide semiconductor layer over an insulating layer;

a first buffer layer having n-type conductivity on and in contact with the oxide semiconductor layer;

a second buffer layer having n-type conductivity on and in contact with the oxide semiconductor layer;

a source electrode layer on the first buffer layer, wherein the first buffer layer extends beyond an inner side edge of the source electrode;

a drain electrode layer on the second buffer layer, wherein the second buffer layer extends beyond an inner side edge of the drain electrode;

a gate insulating layer over the source electrode layer and the drain electrode layer, the gate insulating layer being in contact with the oxide semiconductor layer; and

a gate electrode layer over the gate insulating layer, the gate electrode layer overlapping with the oxide semiconductor layer,

wherein inner side edges of the first buffer layer and the second buffer layer are tapered.

2. The semiconductor device according to claim 1, wherein each of the source electrode layer and the drain electrode layer is any of a single film, an alloy film, and a layered film including any of the single film and the alloy film.

3. The semiconductor device according to claim 2, wherein each of the single film and the alloy film comprises an element selected from aluminum, chromium, copper, tantalum, titanium, molybdenum, and tungsten.

4. The semiconductor device according to claim 1, wherein the buffer layer further comprises one or more elements selected from aluminum, gallium, and silicon.

5. The semiconductor device according to claim 1, wherein the oxide semiconductor layer comprises at least one element selected from In, Ga, Sn, Zn, Al, Mg, Hf, and lanthanoid.

6. The semiconductor device according to claim 1, wherein the gate insulating layer contains oxygen.

7. The semiconductor device according to claim 1, wherein each of the source electrode layer and the drain electrode layer provides steps over the buffer layer.

8. The semiconductor device according to claim 1, wherein a taper angle of the inner side edges of the first buffer layer and the second buffer layer is smaller than a taper angle of the inner side edges of the source electrode layer and the drain electrode layer.

9. The semiconductor device according to claim 1, wherein the buffer layer comprises a material selected from titanium oxide, titanium niobium oxide, molybdenum oxide, tungsten oxide, magnesium oxide, calcium oxide, and gallium oxide.

10. The semiconductor device according to claim 1, wherein the gate electrode layer overlaps with the source electrode layer and the drain electrode layer.

11. A semiconductor device comprising:

an oxide semiconductor layer over an insulating layer;

a first buffer layer having n-type conductivity on and in contact with the oxide semiconductor layer;

a second buffer layer having n-type conductivity on and in contact with the oxide semiconductor layer;

a source electrode layer on the first buffer layer, wherein the first buffer layer extends beyond an inner side edge of the source electrode;

a drain electrode layer on the second buffer layer, wherein the second buffer layer extends beyond an inner side edge of the drain electrode;

a gate insulating layer over the source electrode layer and the drain electrode layer, the gate insulating layer being in contact with the oxide semiconductor layer; and

a gate electrode layer over the gate insulating layer, the gate electrode layer overlapping with the oxide semiconductor layer,

wherein inner side edges of the first buffer layer and the second buffer layer are tapered, and

wherein a surface portion of the oxide semiconductor layer between the first buffer layer and the second buffer layer is etched.

12. The semiconductor device according to claim 11, wherein each of the source electrode layer and the drain electrode layer is any of a single film, an alloy film, and a layered film including any of the single film and the alloy film.

13. The semiconductor device according to claim 12, wherein each of the single film and the alloy film comprises an element selected from aluminum, chromium, copper, tantalum, titanium, molybdenum, and tungsten.

14. The semiconductor device according to claim 11, wherein the buffer layer further comprises one or more elements selected from aluminum, gallium, and silicon.

15. The semiconductor device according to claim 11, wherein the oxide semiconductor layer comprises at least one element selected from In, Ga, Sn, Zn, Al, Mg, Hf, and lanthanoid.

16. The semiconductor device according to claim 11, wherein the gate insulating layer contains oxygen.

17. The semiconductor device according to claim 11, wherein each of the source electrode layer and the drain electrode layer provides steps over the buffer layer.

18. The semiconductor device according to claim 11, wherein a taper angle of the inner side edges of the first buffer layer and the second buffer layer is smaller than a taper angle of the inner side edges of the source electrode layer and the drain electrode layer.

19. The semiconductor device according to claim 11, wherein the buffer layer comprises a material selected from titanium oxide, titanium niobium oxide, molybdenum oxide, tungsten oxide, magnesium oxide, calcium oxide, and gallium oxide.

20. The semiconductor device according to claim 11, wherein the gate electrode layer overlaps with the source electrode layer and the drain electrode layer.