| CPC H10F 39/1865 (2025.01) | 19 Claims |
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1. A pixel cell, disposed on a semiconductor substrate having a front surface and a backside surface, the pixel cell comprising:
a photodiode disposed in the semiconductor substrate, the photodiode comprising a photodiode region of a second conductive type opposite to a first conductive type of the semiconductor substrate;
a first doped region disposed in the semiconductor substrate, the first doped region extending from the front surface to have a first junction depth in the semiconductor substrate along a depth direction perpendicular to the front surface, wherein the first doped region is of the second conductive type;
a second doped region of the second conductive type extending from the front surface to have a second junction depth in the semiconductor substrate, the second junction depth being less than the first junction depth with respect to the front surface, wherein the second doped region is coupled to the first doped region, and the second doped region is surrounded by the first doped region; and
a transfer gate, selectively coupling the photodiode to the first doped region, the transfer gate configured to transfer image charges from the photodiode to the first doped region, the transfer gate having a planar gate electrode on the front surface of the semiconductor substrate and at least one vertical gate electrode, the at least one vertical gate electrode extending from the planar gate electrode, along the depth direction, a gate depth into the semiconductor substrate;
wherein the first junction depth is greater than the gate depth;
wherein both the first doped region and the second doped region are distanced from the photodiode region of the photodiode;
wherein a first concentration of the first doped region is less than a second concentration of the second doped region.
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