The present invention relates to a method for forming a via in a substrate. The method includes the following steps: (a) providing a substrate; (b) forming a groove that has a side wall and a bottom wall on a first surface of the substrate; (c) forming a first conductive metal on the side wall and the bottom wall of the groove so as to form a central groove; (d) forming a center insulating material in the central groove; (e) forming an annular groove that surrounds the first conductive metal on the first surface of the substrate; (f) forming a first insulating material in the annular groove; and (g) removing part of the substrate to expose the first conductive metal, the center insulating material and the first insulating material.