The invention discloses a method for improving the height uniformity of a
device grid electrode, and the method comprises the steps: S1, providing a substrate, forming an
oxide layer on the surface of the substrate, and forming a plurality of projection structures which are arranged at intervals on the substrate; s2, a grid
polycrystalline silicon layer is deposited on the
oxide layer, the grid
polycrystalline silicon layer is higher than the protruding structure, and a first low-
lying area is formed on the
surface layer of the grid
polycrystalline silicon layer; s3, depositing a
silicon nitride layer on the surface of the grid polycrystalline
silicon layer, wherein a second low-
lying area is formed on the
surface layer of the
silicon nitride layer; s4, a protection polycrystalline silicon layer is formed on the
silicon nitride layer, a third low-
lying area is formed on the
surface layer of the protection polycrystalline silicon layer, and the third low-lying area is located above the second low-lying area; s5, performing a chemical mechanical
grinding process on the protective polycrystalline silicon layer, and stopping the chemical mechanical
grinding process on the surface of the
silicon nitride layer; and S6, carrying out an etchback process until the thickness of the residual gate polycrystalline silicon layer reaches the target thickness. According to the scheme, the height uniformity of the grid
electrode of the device can be improved.