the overlying polysilicon layers are patterned by anisotropic etching this residue often referred to as stringers or rails can occur when polysilicon gate electrodes and word lines are formed on product such as dram and sram chips referring now more specifically to the objective of the first embodiment of this invention the method of eliminating this problem by forming gradually sloping edges on the field oxide by implanting ions and etching the field oxide structure is now described in detail still referring to fig2 the substrate 10 is placed in an ion implant chamber and the chamber is typically evacuated to a pressure of less than 10 6 torr the substrate is then positioned so that the tilt angle is preferably between about 0 to 60 degrees and more specifically at a tilt angle of 45 degrees the tilt angle being the angular distance in degrees between a line drawn perpendicular to the substrate surface generally referred to as the normal to the surface and the ion beam direction the substrate is then rotated about an axis which is also normal to the substrate surface the substrate having the field oxide 12 thereon and the silicon nitride layer 16 still protecting the device area is then implanted with arsenic as 75 ion having a preferred dose of greater than 2 e 13 ions cm 2 and at an ion implant energy of between about 50 to 100 kev however the ion implant energy should not exceed 100 kev so as to avoid forming a trench in the field oxide at the silicon nitride edge which can cause device problems at a later processing steps alternatively the substrate can also be implanted with phosphorus.