| CPC H01L 31/02327 (2013.01) [H01L 31/035281 (2013.01); H01L 31/103 (2013.01); H01L 31/1804 (2013.01)] | 12 Claims |

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1. A device for optical sensing, comprising:
a substrate comprising a trench;
a photodetector disposed in the substrate and next to the trench;
a first dielectric layer disposed on the substrate and comprising a through hole connected to the trench; and
a reflector disposed on the first dielectric layer and extending into the trench through a sidewall of the through hole, wherein the reflector exposes a side of the trench close to the photodetector.
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