a polycrystalline memory structure is described for improving reliability and yield of devices employing polycrystalline memory materials comprising a polycrystalline memory layer , which has crystal grain boundaries forming gaps between adjacent crystallites overlying a substrate . an insulating material is located at least partially within the gaps to at least partially block the entrance to the gaps . a method of forming a polycrystalline memory structure is also described . a layer of material is deposited and annealed to form a polycrystalline memory material having gaps between adjacent crystallites . an insulating material is deposited over the polycrystalline memory material to at least partially fill the gaps , thereby blocking a portion of each gap .