| CPC H10D 62/124 (2025.01) [H10D 8/041 (2025.01); H10D 62/40 (2025.01)] | 18 Claims |

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1. A method comprising:
providing a substrate having a first conductivity type, and having a first surface and a second surface opposite to the first surface;
diffusing impurities into the substrate to form a first diffusion layer having the first conductivity type and a second diffusion layer having a second conductivity type, wherein the second diffusion layer is formed by forming an upper diffusion layer having the first conductivity type, removing at least a portion of the upper diffusion layer and inverting the rest of the upper diffusion layer from the first conductivity type to the second conductivity type;
forming a plurality of diffusion regions having the first conductivity in the second diffusion layer having the second conductivity type;
forming a square groove ring in the substrate, wherein:
the square groove ring extends through the second diffusion layer and the substrate, and extends into the first diffusion layer;
forming a glass layer over the square groove ring;
forming a first electrode layer on the first diffusion layer; and
forming a second electrode layer on the second diffusion layer, wherein the second electrode layer is in contact with the plurality of diffusion regions.
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