Semiconductor device

• US 9,219,161 B2
• Filed: 10/23/2013
• Issued: 12/22/2015
• Est. Priority Date: 10/24/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Mandala, Victor A
• Application Number:
  US14/061,427
• Publication Number:
  US 20140110706A1
• Time in Patent Office: 790 Days
• US Class Current: 1/1
• 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 29/66969 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 29/78645 with multiple gate
• 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 29/78696 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 semiconductor device having a structure which can prevent a decrease in electrical characteristics, which becomes more significant with miniaturization of a transistor, is provided. In addition, a highly reliable semiconductor device is provided. The semiconductor device includes a first gate electrode layer, a second gate electrode layer, and a third gate electrode layer, which are each provided separately. The first gate electrode layer overlaps with an oxide semiconductor layer. The second gate electrode layer partly covers one end portion of the oxide semiconductor layer in the channel width direction. The third gate electrode layer partly covers the other end portion of the oxide semiconductor layer in the channel width direction.

Claims

1. A semiconductor device comprising:

an oxide semiconductor layer over a substrate;

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

a gate insulating film over the oxide semiconductor layer, the source electrode, and the drain electrode; and

a first gate electrode, a second gate electrode, and a third gate electrode over the gate insulating film,

wherein the first gate electrode, the second gate electrode, and the third gate electrode are separated from one another,

wherein the first gate electrode overlaps with the oxide semiconductor layer,

wherein the second gate electrode partly covers one end portion of the oxide semiconductor layer in a channel width direction, and

wherein the third gate electrode partly covers the other end portion of the oxide semiconductor layer in the channel width direction.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor layer comprises a first oxide semiconductor layer, a second oxide semiconductor layer, and a third oxide semiconductor layer which are stacked in this order from the substrate.

3. The semiconductor device according to claim 2, wherein a bottom of a conduction band of each of the first oxide semiconductor layer and the third oxide semiconductor layer is closer to a vacuum level than a bottom of a conduction band of the second oxide semiconductor layer by 0.05 eV or more and 2 eV or less.

4. The semiconductor device according to claim 2,

wherein the first oxide semiconductor layer, the second oxide semiconductor layer, and the third oxide semiconductor layer are each an In-M-Zn oxide (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf), and

wherein an atomic ratio of M to In in each of the first oxide semiconductor layer and the third oxide semiconductor layer is higher than an atomic ratio of M to In in the second oxide semiconductor layer.

5. The semiconductor device according to claim 1,

the source electrode comprising:

a first source electrode layer in contact with the oxide semiconductor layer; and

a second source electrode layer covering the first source electrode layer and in contact with the oxide semiconductor layer, and

the drain electrode comprising;

a first drain electrode layer in contact with the oxide semiconductor layer; and

a second drain electrode layer covering the first drain electrode layer and in contact with the oxide semiconductor layer.

6. The semiconductor device according to claim 5,

wherein the first source electrode layer and the first drain electrode layer include a first material, and the second source electrode layer and the second drain electrode layer include a second material, and

wherein one of the first material and the second material is Al, Cr, Cu, Ta, Ti, Mo, W, or an alloy material containing any of them as its main component, and the other of the first material and the second material is tantalum nitride, titanium nitride, ruthenium, or an alloy material containing any of them as its main component.

7. The semiconductor device according to claim 5, wherein the first gate electrode overlaps with neither the first source electrode layer nor the first drain electrode layer.

8. A semiconductor device comprising:

a first oxide semiconductor layer over a substrate;

a second oxide semiconductor layer over the first oxide semiconductor layer;

a first source electrode layer and a first drain electrode layer in contact with the second oxide semiconductor layer;

a third oxide semiconductor layer over the second oxide semiconductor layer, the first source electrode layer, and the first drain electrode layer;

a second source electrode layer covering the first source electrode layer and in contact with the first source electrode layer and the third oxide semiconductor layer;

a second drain electrode layer covering the first drain electrode layer and in contact with the first drain electrode layer and the third oxide semiconductor layer;

a gate insulating film over the third oxide semiconductor layer, the second source electrode layer, and the second drain electrode layer; and

a first gate electrode, a second gate electrode, and a third gate electrode over the gate insulating film,

wherein the first gate electrode, the second gate electrode, and the third gate electrode are separated from one another,

wherein the first gate electrode overlaps with the first oxide semiconductor layer and the second oxide semiconductor layer,

wherein the second gate electrode partly covers one end portion of each of the first oxide semiconductor layer and the second oxide semiconductor layer in a channel width direction, and

wherein the third gate electrode partly covers the other end portion of each of the first oxide semiconductor layer and the second oxide semiconductor layer in the channel width direction.

9. The semiconductor device according to claim 8, wherein a bottom of a conduction band of each of the first oxide semiconductor layer and the third oxide semiconductor layer is closer to a vacuum level than a bottom of a conduction band of the second oxide semiconductor layer by 0.05 eV or more and 2 eV or less.

10. The semiconductor device according to claim 8,

wherein the first oxide semiconductor layer, the second oxide semiconductor layer, and the third oxide semiconductor layer are each an In-M-Zn oxide (M is Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf), and

wherein an atomic ratio of M to In in each of the first oxide semiconductor layer and the third oxide semiconductor layer is higher than an atomic ratio of M to In in the second oxide semiconductor layer.

11. The semiconductor device according to claim 8,

wherein the first source electrode layer and the first drain electrode layer include a first material, and the second source electrode layer and the second drain electrode layer include a second material, and

wherein one of the first material and the second material is Al, Cr, Cu, Ta, Ti, Mo, W, or an alloy material containing any of them as its main component, and the other of the first material and the second material is tantalum nitride, titanium nitride, ruthenium, or an alloy material containing any of them as its main component.

12. The semiconductor device according to claim 8, wherein the first gate electrode overlaps with neither the first source electrode layer nor the first drain electrode layer.