A method for fabricating flash memory devices, e.g., NAND, NOR, is provided. The method includes providing a semiconductor substrate. The method includes forming a second polysilicon layer overlying a plurality of floating gate structures to cause formation of an upper surface provided on the second polysilicon layer. The upper surface has a first recessed region and a second recessed region. The method includes depositing a doped dielectric material overlying the upper surface to fill the first recessed region and the second recessed region to form a second upper surface region and cover a first elevated region, a second elevated region, and a third elevated region. The method subjects the second upper surface region to a chemical mechanical polishing process to remove the first elevated region, the second elevated region, and the third elevated region to cause formation of a substantially planarized second polysilicon layer free from the fill material.