| CPC H01L 29/0649 (2013.01) | 12 Claims |

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1. A semiconductor device, comprising:
a substrate;
two shallow trench isolation disposed within the substrate, wherein each of the shallow trench isolation having multi-stacked layers, wherein the layers of the multi-stacked layers comprise a first dielectric layer, a second dielectric layer and a third dielectric layer stacked from bottom to top, and a topmost surface of the first dielectric layer is lower than a topmost surface of the substrate and a topmost surface of the second dielectric layer;
a groove between the second dielectric layer and the substrate;
a fourth dielectric layer disposed in the groove and directly contacting the top surfaces of the first dielectric layer and the substrate; and
a polysilicon material layer fills up the groove, a topmost surface of the polysilicon material layer is lower than the topmost surface of the substrate.
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