A structure of 3D memory comprises a plurality of stacking layers and a plurality of cells. The stacking layers are arranged in a three-dimensional array and disposed parallel to each other on a substrate, and the stacking layers comprises a plurality of stacking memory layers. The cells comprises a first group of cells (such as m of cells) for storing information data and a second group of cells (such as n of cells) for storing ECC (error checking and correcting) spare bits. All of the first group and the second group of cells are read out at the same time for performing an ECC function. The ECC spare bits in the 3D memory according to the present disclosure can be constructed at the same physical layer or at the different physical layers. The embodiments can be implemented, but not limited, by a vertical-gate (VG) structure or a finger VG structure.