A frontside illuminated image sensor, comprising: an array of pixels, wherein a plurality of the pixels each have: a doped silicon substrate (101, 310, 410) having an incident side for receiving incident light (150, 370, 470), the doped silicon substrate having a concave surface (330, 430) at its light-incident side, the concave surface having multiple angles of reflection; a deposition layer (350, 450) disposed over the doped silicon substrate; a stack of multiple layers (108, M1, 110, M2) disposed over the deposition layer; a photosensitive region (102, 104, 106, 360, 460) disposed within the deposition layer; and a reflector (140, 340, 440) disposed at an interface between and in contact with the doped silicon substrate and the deposition layer; the deposition layer having a light incident side facing the stack of multiple layers and an opposite side facing the doped silicon substrate, the deposition layer disposed over the concave surface of the doped silicon substrate and being a single layer that is distinct from the doped silicon substrate; wherein the reflector is arranged between and in contact with the doped silicon substrate and a surface portion of the deposition layer that is opposed to the light incident side and conforms to the concave surface of the doped silicon substrate, such that, during operation, light incident on the multiple angles of reflection of the concave surface of the reflector after passing through the stack of multiple layers and the photosensitive region is reflected back towards the photosensitive region. an array of pixels, wherein a plurality of the pixels each have: a doped silicon substrate (101, 310, 410) having an incident side for receiving incident light (150, 370, 470), the doped silicon substrate having a concave surface (330, 430) at its light-incident side, the concave surface having multiple angles of reflection; a deposition layer (350, 450) disposed over the doped silicon substrate; a stack of multiple layers (108, M1, 110, M2) disposed over the deposition layer; a photosensitive region (102, 104, 106, 360, 460) disposed within the deposition layer; and a reflector (140, 340, 440) disposed at an interface between and in contact with the doped silicon substrate and the deposition layer; the deposition layer having a light incident side facing the stack of multiple layers and an opposite side facing the doped silicon substrate, the deposition layer disposed over the concave surface of the doped silicon substrate and being a single layer that is distinct from the doped silicon substrate; wherein the reflector is arranged between and in contact with the doped silicon substrate and a surface portion of the deposition layer that is opposed to the light incident side and conforms to the concave surface of the doped silicon substrate, such that, during operation, light incident on the multiple angles of reflection of the concave surface of the reflector after passing through the stack of multiple layers and the photosensitive region is reflected back towards the photosensitive region. a doped silicon substrate (101, 310, 410) having an incident side for receiving incident light (150, 370, 470), the doped silicon substrate having a concave surface (330, 430) at its light-incident side, the concave surface having multiple angles of reflection; a deposition layer (350, 450) disposed over the doped silicon substrate; a stack of multiple layers (108, M1, 110, M2) disposed over the deposition layer; a photosensitive region (102, 104, 106, 360, 460) disposed within the deposition layer; and a reflector (140, 340, 440) disposed at an interface between and in contact with the doped silicon substrate and the deposition layer; the deposition layer having a light incident side facing the stack of multiple layers and an opposite side facing the doped silicon substrate, the deposition layer disposed over the concave surface of the doped silicon substrate and being a single layer that is distinct from the doped silicon substrate; wherein the reflector is arranged between and in contact with the doped silicon substrate and a surface portion of the deposition layer that is opposed to the light incident side and conforms to the concave surface of the doped silicon substrate, such that, during operation, light incident on the multiple angles of reflection of the concave surface of the reflector after passing through the stack of multiple layers and the photosensitive region is reflected back towards the photosensitive region.