3-stage method for forming deep trench structure and deep trench capacitor

A method for forming a trench capacitor comprising the steps of:

• providing a substrate;
• forming a mask layer of a predetermined pattern on the substrate to expose a portion of the substrate, the mask layer comprising an oxide layer;
• forming a first trench in the exposed portion of the substrate, the first trench having a first depth;
• forming a second trench in the first trench downward, the second trench having a second depth greater than the first depth;
• forming a third trench in the second trench downward, the third trench having a third depth greater than the second depth;
• forming a conductive diffusion region in the substrate of the periphery of the third trench;
• removing the first protection layer and the second protection layer;
• forming a dielectric layer on the surfaces of the overall structure;
• filling all trenches with a first conductive layer, and making the height of the first conductive layer greater than the bottom of the oxide layer of the mask layer;
• removing a portion of the first conductive layer to make the height of the left first conductive layer greater than the bottom of the insulation layer on the surface of the second trench;
• and
• removing the dielectric layer not covered by the first conductive layer.