A pixel includes a semiconductor substrate, a photodiode region, a floating diffusion region, and a dielectric layer. The substrate has a top surface forming a trench lined by the dielectric layer, and having a trench depth relative to a planar region of the top surface. The photodiode region is in the substrate and includes a bottom photodiode section beneath the trench and a top photodiode section adjacent to the trench, adjoining the bottom photodiode section, and extending toward the planar region to a photodiode depth less than the trench depth. The floating diffusion region is adjacent to the trench and has a junction depth less than the trench depth. A top region of the dielectric layer is between the planar region and the junction depth. A bottom region of the dielectric layer is between the photodiode depth and the trench depth, and thicker than the top region.