Deep trench capacitor and manufacturing method thereof

The invention provides a deep trench capacitor and a manufacturing method thereof, and the method comprises the steps: providing a substrate, and forming a deep trench in the substrate; forming an oxide layer and a polycrystalline silicon layer which are stacked in the deep trench and on the surface of the substrate; etching the stacked oxide layer and polycrystalline silicon layer to form an opening by taking the substrate and the polycrystalline silicon layer as etching stop layers in sequence; forming side walls at two ends of the opening; depositing to form a metal front dielectric layer, wherein the upper surface of the metal front dielectric layer is higher than the top surface of the side wall; etching the pre-metal dielectric layer to form a contact hole, and filling metal in the contact hole; and forming a metal layer on the surfaces of the metal front dielectric layer and the contact hole, wherein the metal layer is connected with the polycrystalline silicon layer through the contact hole and the su