Manufacturing method of deep trench isolation structure with ultrahigh depth-to-width ratio

The invention provides a manufacturing method of a deep trench isolation structure with an ultrahigh depth-to-width ratio, and the method comprises the steps: providing a substrate, sequentially forming a first dielectric layer, a first silicon nitride layer, a second dielectric layer, a second silicon nitride layer and a third dielectric layer on the substrate, and forming a shallow trench isolation structure in the first silicon nitride layer, the first dielectric layer and the substrate; etching the third dielectric layer, the second silicon nitride layer, the second dielectric layer, the shallow trench isolation structure and the substrate to form a trench of the deep trench isolation structure; forming a lining oxide layer on the inner wall of the groove; depositing a first high-density plasma film layer in the groove; depositing a high aspect ratio process film layer in the groove to form an air gap; and depositing a second high-density plasma film layer in the groove. According to the invention, the di