Method for fabricating semiconductor device

1. A method for fabricating a semiconductor device, comprising:

preparing a substrate defined as a first region, a second region and a third region;

forming a stack structure on the substrate;

exposing the substrate of the first region by etching the stack structure and simultaneously forming a plurality of first floating gates on the second region;

forming second inter-poly dielectric layers on sidewalls of the first floating gates and a sidewall of the stack structure remaining on the third region;

forming a gate oxide layer on the substrate of the second region exposed in both sides of the first floating gates and on the substrate of the first region;

forming a second polysilicon layer over the gate oxide layer, the first floating gates and the stack structure;

forming a gate electrode on the substrate of the first region by etching the second polysilicon layer and the gate oxide layer and simultaneously forming control gates on both sidewalls of the second inter-poly dielectric layers existing on the substrate of the second region; and

forming second floating gates and second control gates by etching the second polysilicon layer, the second inter-poly silicon layer, the stack structure on the substrate of the third region.

2. The method of claim 1 , wherein the stack structure includes a first insulation layer, a first polysilicon layer and a first inter-poly dielectric layer.

3. The method of claim 1 , wherein the first region is a where a transistor for a logic device will be formed, a second region is where an electrical erasable programmable read only memory (EEPROM) cell will be formed, and a third region is where a flash memory cell will be formed.

4. The method of claim 1 , after the forming of the plurality of second floating gates and the second control gates further including forming a plurality of source/drain regions in the substrate exposed by the gate electrode, the first control gates and the second control gates.

5. The method of claim 2 , wherein the first insulation layer is an oxynitride layer including nitrogen.

6. The method of claim 2 , wherein the first insulation layer is formed in a thickness ranging from approximately 50 Å to approximately 200 Å.

7. The method of claim 2 , wherein the first polysilicon layer is formed in a thickness ranging from approximately 500 Å to approximately 5,000 Å.

8. The method of claim 2 , wherein the first inter-poly dielectric layer is formed in a structure of an oxide layer, a nitride layer and an oxide layer (ONO).

9. The method of claim 2 , after the depositing of the first inter-poly dielectric layer further including forming a second insulation layer on the first inter-poly dielectric layer.

10. The method of claim 9 , wherein the second insulation layer includes one selected from the group consisting of an oxide layer, a nitride layer, an oxynitride layer, and a stack layer thereof.

11. The method of claim 9 , wherein the forming of the plurality of first floating gates includes:

etching the second insulation layer and the first inter-poly dielectric layer by using a mask;

removing the mask; and

etching the first polysilicon layer and the first insulation layer through an etching process by using the etched second insulation layer as an etch mask.

12. The method of claim 1 , wherein the second inter-poly dielectric layers are formed in a structure of an oxide layer, a nitride layer and an oxide layer (ONO).

13. The method of claim 1 , wherein the gate oxide layer is more thickly formed on the substrate of the first region than on the substrate of the second region.

14. The method of claim 13 , wherein the gate oxide layer formed on the substrate of the first region has a thickness ranging from approximately 15 Å to approximately 200 Å.

15. The method of claim 13 , wherein the gate oxide layer formed on the substrate of the second region has a thickness ranging from approximately 50 Å to approximately 500 Å.

16. The method of claim 13 , wherein the gate oxide layer formed on the substrate of the second region is formed between the respective first control gate and the substrate.

17. The method of claim 1 , wherein the second polysilicon layer is formed in a thickness ranging from approximately 500 Å to approximately 5,000 Å.

18. The method of claim 1 , after the forming the plurality of second control gates further including forming a plurality of spacers on sidewalls of the first control gates, the second floating gates and the second control gates.

19. The method of claim 4 , wherein the forming of the plurality of source/drain regions includes:

forming a plurality of lowly doped junction regions in the substrate of the first region to the third region by performing a lightly doped drain (LDD) ion-implantation process;

forming a third insulation layer over the gate electrode, the first control gates, and the second control gates;

forming a plurality of spacers on sidewalls of the gate electrode, the first control gates, the second floating gates and the second control gates; and

forming a plurality of highly doped junction regions in both sides of the spacers in the substrate of the first region to the third region through performing a highly doped source/drain ion-implantation process using the spacers as a mask.

20. The method of claim 19 , wherein the lowly doped junction regions comprise an N-type, an impurity ion selected from the group consisting of arsenic (As), phosphorous (P) and indium (In) is used.

21. The method of claim 19 , wherein the lowly doped junction regions comprise a P-type, an impurity ion selected from the group consisting of boron (B), BF 2 and antimony (Sb) is used.

22. The method of claim 19 , wherein the third insulation layer includes one selected from the group consisting of an oxide layer, a nitride layer and a combination thereof.