Method for improving capacitance in dram capacitors and devices formed

Abstract

The present invention discloses a method for forming a DRAM capacitor that has improved charge capacity and a DRAM capacitor formed by such method. The method can be carried out by first depositing an oxide layer on a lower polysilicon electrode layer on a semiconductor structure, then polishing the top surface of the oxide layer to form an uneven surface which provides increased surface area, and then anisotropically etching away the oxide layer while reproducing the uneven surface of the oxide layer onto the lower polysilicon electrode layer such that an increased charge capacity can be realized. The anisotropic etch chemistry should be selected such that the etchant etches away both the oxide layer and the polysilicon layer, and preferably, the etchant should have a higher selectivity toward polysilicon and a lower selectivity toward oxide such that the oxide layer can be completely removed while only a portion of the polysilicon layer is removed to form the uneven surface.