We have developed a flat device structure, which we call “FLAT”, with no isolation grooves/ridges and no Si substrate etching in the imaging area of the CMOS Image Sensor (CIS). We employed this FLAT structure to achieve a 1.12 μm pitch pixel CIS with a 1.25 transistor/pixel architecture and excellent image quality. It uses FLAT transistors (Trs) that generate greatly-reduced 1/f noise, and FLAT isolators (Isos) that increase the saturation capacity (Qs) due to increasing both effective photodiode (PD) area and PD potential under low dark current.