The present disclosure relates to a solid-state imaging element, a manufacturing method, and an electronic device capable of further improving quality. A flattening film is formed so as to fill a recessed portion of a semiconductor substrate having a pixel region in which a plurality of pixels is arranged in an array, a recessed region is formed in the flattening film by hollowing out a region corresponding to the pixel region, and a color filter layer is formed in the recessed region. In addition, an on-chip lens layer is formed on a plane including the flattening film and the color filter layer. The present technology is applicable, for example, to a CMOS image sensor.