FIELD EFFECT TRANSISTOR

• US 20110309411A1
• Filed: 06/08/2011
• Published: 12/22/2011
• Est. Priority Date: 06/16/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: TAKEMURA, Yasuhiko
• Granted Patent: US 9,209,314 B2
• Time in Patent Office: Days
• US Class Current: 257/192
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/823814 with a particular manufacturing method of the source or drain structures, e.g. specific source or drain implants or silicided source or drain structures or raised source or drain structures
• 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 29/41725 Source or drain electrodes for field effect devices with monocrystalline semiconductor on source/drain region H01L29/0843
• 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 29/7869 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

An insulating film is provided over one surface of a first semiconductor layer including a first oxide semiconductor including indium as a main component, and a second semiconductor layer including an i-type second oxide semiconductor is provided in contact with the other surface. The energy difference between a vacuum level and a Fermi level in the second oxide semiconductor is larger than that in the first oxide semiconductor. In the first semiconductor layer, a region in the vicinity of the junction surface with the second oxide semiconductor which satisfies the above condition is a region having an extremely low carrier concentration (a quasi-i-type region). By using the region as a channel, the off-state current can be reduced. Further, a drain current of the FET flows through the first oxide semiconductor having a high mobility; accordingly, a large amount of current can be extracted.

Claims

1. A field effect transistor comprising:

a first semiconductor layer including a first oxide semiconductor,

wherein the first oxide semiconductor includes indium as a main component;

a second semiconductor layer in contact with one surface of the first semiconductor layer,

wherein the second semiconductor layer includes a second oxide semiconductor,

wherein the second oxide semiconductor is an i-type oxide semiconductor, and

wherein a bandgap of the second oxide semiconductor is wider than a bandgap of the first oxide semiconductor;

a conductive layer adjacent to the other surface of the first semiconductor layer; and

an insulating layer between the conductive layer and the first semiconductor layer,

wherein an energy difference between a vacuum level of the second oxide semiconductor and a Fermi level of the second oxide semiconductor is larger than an energy difference between a vacuum level of the first oxide semiconductor and a Fermi level of the first oxide semiconductor.

2. The field effect transistor according to claim 1,

wherein the first semiconductor layer has a thickness of more than or equal to 0.1 nm and less than or equal to 100 nm.

3. The field effect transistor according to claim 1,

wherein the second semiconductor layer has a thickness of more than or equal to 10 nm and less than or equal to 100 nm.

4. The field effect transistor according to claim 1,

wherein the second semiconductor layer is sandwiched between and in contact with the first semiconductor layer and an insulating film including an oxide including aluminum as a main component, and

wherein the oxide has a bandgap of 8 eV or more.

5. The field effect transistor according to claim 1,

wherein the first semiconductor layer is sandwiched between and in contact with the second semiconductor layer and an insulating film including an oxide including aluminum as a main component, and

wherein the oxide has a bandgap of 8 eV or more.

6. The field effect transistor according to claim 1,

wherein the second oxide semiconductor has a bandgap of 6 eV or less.

7. The field effect transistor according to claim 1,

wherein the conductive layer functions as a gate electrode, and

wherein the insulating layer functions as a gate insulating film.

8. A field effect transistor comprising:

a first semiconductor layer including a first oxide semiconductor,

wherein the first oxide semiconductor includes indium as a main component;

a second semiconductor layer in contact with one surface of the first semiconductor layer,

wherein the second semiconductor layer includes a second oxide semiconductor,

wherein the second oxide semiconductor is an i-type oxide semiconductor,

wherein the second oxide semiconductor includes gallium as a main component, and

wherein a bandgap of the second oxide semiconductor is wider than a bandgap of the first oxide semiconductor;

a conductive layer adjacent to the other surface of the first semiconductor layer; and

an insulating layer between the conductive layer and the first semiconductor layer.

9. The field effect transistor according to claim 8,

wherein the first semiconductor layer has a thickness of more than or equal to 0.1 nm and less than or equal to 100 nm.

10. The field effect transistor according to claim 8,

wherein the second semiconductor layer has a thickness of more than or equal to 10 nm and less than or equal to 100 nm.

11. The field effect transistor according to claim 8,

wherein the second semiconductor layer is sandwiched between and in contact with the first semiconductor layer and an insulating film including an oxide including aluminum as a main component, and

wherein the oxide has a bandgap of 8 eV or more.

12. The field effect transistor according to claim 8,

wherein the first semiconductor layer is sandwiched between and in contact with the second semiconductor layer and an insulating film including an oxide including aluminum as a main component, and

wherein the oxide has a bandgap of 8 eV or more.

13. The field effect transistor according to claim 8,

wherein the second oxide semiconductor has a bandgap of 6 eV or less.

14. The field effect transistor according to claim 8,

wherein the conductive layer functions as a gate electrode, and

wherein the insulating layer functions as a gate insulating film.

15. A field effect transistor comprising:

a first semiconductor layer including a first oxide semiconductor,

wherein the first oxide semiconductor includes indium as a main component;

a second semiconductor layer in contact with one surface of the first semiconductor layer,

wherein the second semiconductor layer includes a second oxide semiconductor,

wherein the second oxide semiconductor is an i-type oxide semiconductor, and

wherein a percentage of gallium to all elements other than oxygen is 80% or more in the second oxide semiconductor;

a conductive layer adjacent to the other surface of the first semiconductor layer; and

an insulating layer between the conductive layer and the first semiconductor layer.

16. The field effect transistor according to claim 15,

wherein the first semiconductor layer has a thickness of more than or equal to 0.1 nm and less than or equal to 100 nm.

17. The field effect transistor according to claim 15,

wherein the second semiconductor layer has a thickness of more than or equal to 10 nm and less than or equal to 100 nm.

18. The field effect transistor according to claim 15,

wherein the second semiconductor layer is sandwiched between and in contact with the first semiconductor layer and an insulating film including an oxide including aluminum as a main component, and

wherein the oxide has a bandgap of 8 eV or more.

19. The field effect transistor according to claim 15,

wherein the first semiconductor layer is sandwiched between and in contact with the second semiconductor layer and an insulating film including an oxide including aluminum as a main component, and

wherein the oxide has a bandgap of 8 eV or more.

20. The field effect transistor according to claim 15,

wherein the second oxide semiconductor has a bandgap of 6 eV or less.

21. The field effect transistor according to claim 15,

wherein the conductive layer functions as a gate electrode, and

wherein the insulating layer functions as a gate insulating film.