Semiconductor memory device with floating gate

• US 8,575,678 B2
• Filed: 01/04/2012
• Issued: 11/05/2013
• Est. Priority Date: 01/13/2011
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Takemura, Yasuhiko
• Primary Examiner(s): Soward, Ida M
• Application Number:
  US13/343,388
• Publication Number:
  US 20120181597A1
• Time in Patent Office: 671 Days
• Field of Search: 257/316, 257/E29.001
• US Class Current: 257/316
• CPC Class Codes: G11C 16/04 using variable threshold transistors, e.g. FAMOS
• CPC Class Codes: H01L 29/40114 the electrodes comprising a conductor-insulator-conductor-insulator-semiconductor structure
• CPC Class Codes: H01L 29/7881 Programmable transistors with only two possible levels of programmation H01L29/7888 takes precedence

Abstract

To provide a semiconductor memory device having a floating gate which operates with a short channel. A high-work-function compound semiconductor having a work function of greater than or equal to 5.5 eV, such as indium nitride or zinc nitride, is used for the floating gate. Accordingly, the potential barrier of the floating gate insulating film between the substrate and the floating gate is higher than that of a conventional one, so that leakage of electric charge due to a tunnel effect can be reduced even if the thickness of the floating gate insulating film is made small. Since the thickness of the floating gate insulating film can be made small, the channel can be further shortened.

Claims

1. A semiconductor memory device comprising;

a floating gate insulating film;

a floating gate over the floating gate insulating film;

a control gate insulating film over the floating gate; and

a control gate over the control gate insulating film

wherein the floating gate comprises an n-type semiconductor having a work function of greater than or equal to 5.5 eV, and

wherein the floating gate contains nitrogen and one selected from the group consisting of indium and zinc.

2. The semiconductor memory device according to claim 1, wherein a carrier concentration in the floating gate is greater than or equal to 1×

10¹⁹ cm<sup>−

3</sup>.

3. The semiconductor memory device according to claim 1, wherein a thickness of the floating gate insulating film is greater than or equal to 2 nm and less than or equal to 4 nm.

4. The semiconductor memory device according to claim 1, wherein the floating gate contains hydrogen at a concentration of 0.01 atomic % to 10 atomic %.

5. The semiconductor memory device according to claim 1, wherein the floating gate contains oxygen.

6. The semiconductor memory device according to claim 1, wherein the floating gate comprises indium nitride.

7. A semiconductor memory device comprising;

a floating gate insulating film;

a floating gate over the floating gate insulating film;

a control gate insulating film over the floating gate; and

a control gate over the control gate insulating film

wherein the floating gate contains nitrogen at a concentration of greater than or equal to 5 atomic % and less than or equal to 50 atomic %, and one selected from the group consisting of zinc and indium.

8. The semiconductor memory device according to claim 7, wherein a carrier concentration in the floating gate is greater than or equal to 1×

10¹⁹ cm<sup>−

3</sup>.

9. The semiconductor memory device according to claim 7, wherein a thickness of the floating gate insulating film is greater than or equal to 2 nm and less than or equal to 4 nm.

10. The semiconductor memory device according to claim 7, wherein the floating gate contains hydrogen at a concentration of 0.01 atomic % to 10 atomic %.

11. The semiconductor memory device according to claim 7, wherein the floating gate contains oxygen.

12. The semiconductor memory device according to claim 7, wherein a concentration of zinc is greater than or equal to 5 atomic % and less than or equal to 66.7 atomic %.

13. The semiconductor memory device according to claim 7, wherein a concentration of indium is greater than or equal to 5 atomic % and less than or equal to 50 atomic %.

14. A semiconductor memory device comprising;

a semiconductor including a source and a drain;

a floating gate insulating film over the semiconductor; and

a floating gate over the floating gate insulating film,

wherein the semiconductor is a material whose electron affinity is 3.5 eV to 4.5 eV and whose band gap is equal to or less than 1.5 eV, and

wherein the floating gate comprises an n-type semiconductor having a work function of greater than or equal to 5.5 eV.

15. The semiconductor memory device according to claim 14, wherein a carrier concentration in the floating gate is greater than or equal to 1×

10¹⁹ cm<sup>−

3</sup>.

16. The semiconductor memory device according to claim 14, wherein a thickness of the floating gate insulating film is greater than or equal to 2 nm and less than or equal to 4 nm.

17. The semiconductor memory device according to claim 14, wherein the floating gate contains hydrogen at a concentration of 0.01 atomic % to 10 atomic %.

18. The semiconductor memory device according to claim 14, wherein the floating gate contains oxygen.

19. The semiconductor memory device according to claim 14, wherein a impurity concentration of the semiconductor is less than or equal to 1×

10¹⁵ cm<sup>−

3</sup>.

20. The semiconductor memory device according to claim 14, wherein halo regions are provided in contact with the source and the drain.