is planarized by cmp selective to oxide the cmp polish attacks the raised portion of the poly first removing material therefrom as more and more material from the raised region is removed the surface of the poly becomes more planar the cmp continues until the surface of the oxide layer 160 in the raised region is exposed thus producing a planar top surface 179 as shown the planar top surface includes poly and oxide regions referring to fig1 e an anisotropic etch selective to poly and nitride is performed to remove the exposed oxide material the etch for example is a reactive ion etch rie the nitride layer 140 on the surface of the mesa serves as an etch stop as such the oxide is removed exposing the nitride layer the portions 181 of the oxide protected by the poly remains due to the fact that the rie is anisotropic in fig1 f the poly is removed by for example a dry etch after the rie this leaves the non conformal layer exposed along with the nitride layer 140 over the wide active region 112 also the oxide fence 181 remains near the etch of the wide active region as can be seen the relative amount of oxide material that needs to the removed in the region over the narrow active area is about the same amount as that over the wide active region although the fences 181 are relatively higher than the triangles 163 the fences are easily removed by the cmp since they are quite thin this enables the cmp to planarize the surface of the non conformal layer 160 using the nitride 140 as.