Semiconductor device and manufacturing method thereof

1. A method for manufacturing a semiconductor device, the method comprising:

etching a first trench in a peripheral region of a substrate;

filling the first trench with a first dielectric material to form a first isolation feature in the first trench;

recessing a cell region of the substrate after filling the first trench with the first dielectric material;

forming a second isolation feature in the cell region of the substrate after recessing the cell region of the substrate;

forming a plurality of control gates over the cell region of the substrate; and

forming a gate stack over the peripheral region of the substrate.

2. The method of claim 1 , further comprising:

etching a transition trench in a transition region of the substrate when etching the first trench, wherein the transition region is between the cell region and the peripheral region; and

filling the transition trench with the first dielectric material to form a third isolation feature in the transition trench.

3. The method of claim 2 , further comprising:

forming a fourth isolation feature in the transition region of the substrate when forming the second isolation feature, wherein the fourth isolation feature is connected with the third isolation feature.

4. The method of claim 3 , wherein recessing the cell region of the substrate is performed such that a portion of the transition region of the substrate is recessed, and a sidewall of the third isolation feature is exposed.

5. The method of claim 4 , wherein forming the fourth isolation feature is performed such that the fourth isolation feature is formed in the recessed portion of the transition region of the substrate.

6. The method of claim 1 , further comprising:

forming a mask layer covering the first isolation feature over the peripheral region of the substrate and exposing the cell region of the substrate prior to recessing the cell region of the substrate.

7. The method of claim 6 , wherein forming the second isolation feature comprises:

etching a second trench in the cell region of the substrate;

filling the second trench with a second dielectric material; and

planarizing the second dielectric material until reaching the mask layer that covers the first isolation feature.

8. The method of claim 6 , further comprising:

recessing the second isolation feature after forming the second isolation feature when the mask layer remains covering the first isolation feature.

9. A method for manufacturing a semiconductor device, the method comprising:

forming a first isolation feature in a peripheral region of a substrate;

depositing a floating gate film over the peripheral region and a cell region of the substrate after forming the first isolation feature, wherein a portion of the floating gate film is over a top surface of the first isolation feature;

forming a trench in the floating gate film and the cell region of the substrate;

forming a second isolation feature in the trench;

forming a plurality of control gates over the floating gate film over the cell region of the substrate; and

forming a gate stack over the peripheral region of the substrate.

10. The method of claim 9 , further comprising:

recessing the cell region of the substrate after forming the first isolation feature.

11. The method of claim 9 , further comprising:

forming a first mask layer covering the first isolation feature over the peripheral region of the substrate and exposing the cell region of the substrate prior to depositing the floating gate film, wherein depositing the floating gate film is performed such that the floating gate film is over the first mask layer.

12. The method of claim 11 , wherein forming the trench comprises:

forming a second mask layer over the floating gate film and the cell region of the substrate; and

etching the floating gate film and the cell region of the substrate through the second mask layer.

13. The method of claim 12 , further comprising:

recessing the second isolation feature when the first mask layer remains covering the first isolation feature and the second mask layer covers the floating gate film.

14. The method of claim 12 , further comprising:

removing the first and second mask layers after forming the second isolation feature; and

recessing the second isolation feature after removing the first and second mask layers.

15. The method of claim 9 , further comprising removing the portion of the floating gate film when forming the trench in the floating gate film and the cell region of the substrate.

16. The method of claim 9 , further comprising forming a tunneling film over the substrate prior to depositing the floating gate film, wherein forming the trench is performed such that the trench is formed in the tunneling film.

17. A method for manufacturing a semiconductor device, the method comprising:

etching a first trench in a peripheral region of a substrate;

filling the first trench with a first dielectric material to form a first isolation feature in the first trench, wherein the first isolation feature surrounds a first active region in the peripheral region of the substrate;

etching a second trench in a cell region of the substrate after filling the first trench with the first dielectric material;

filling the second trench with a second dielectric material to form a second isolation feature in the second trench, wherein the second isolation feature surrounds a second active region in the cell region of the substrate; and

forming a control gate over the second active region; and

forming a gate stack over the first active region.

18. The method of claim 17 , wherein filling the second trench with the second dielectric material to form the second isolation feature is performed such that a top surface of the second isolation feature is higher than a top surface of the first isolation feature.

19. The method of claim 18 , further comprising:

recessing the top surface of the second isolation feature prior to forming the control gate, wherein the recessed top surface of the second isolation feature is lower than the top surface of the first isolation feature.

20. The method of claim 17 , further comprising:

etching a first transition trench in a transition region of the substrate when etching the first trench, wherein the transition region is between the cell region and the peripheral region;

filling the first transition trench with the first dielectric material to form a third isolation feature in the first transition trench;

etching a second transition trench in the transition region of the substrate when etching the second trench, wherein a sidewall of the third isolation feature is exposed by the second transition trench; and

filling the second transition trench with the second dielectric material to form a fourth isolation feature in the second transition trench, wherein the fourth isolation feature is connected with the third isolation feature.