Abstract: A method for preventing a contact plug on a semiconductor substrate from being poisoned. A part of the metal layer with a large and flat surface region is removed to result in a plurality of metal layers with smaller surface areas on the substrate. A first dielectric layer is formed on the metal layers. A spin-on-glass layer is formed on the first dielectric layer. The spin-on-glass layer is etched back until the first dielectric layer is exposed. A second dielectric layer is formed on the spin-on-glass layer. At lease an opening is formed to penetrate through the second dielectric layer, the spin-on-glass layer and the first dielectric layer. The opening is filled with a contact plug.

Abstract: A method of forming a contact plug. A dummy pattern with an uneven surface is formed on a region of the substrate. A dielectric layer with an opening exposing a part of the substrate is formed on the dummy pattern and the substrate. A first wiring layer is formed on the dielectric layer and to fill the opening. A sandwich type spin-on-glass layer is formed on the first wiring layer. An opening penetrating through the sandwich type dielectric layer is formed, and the opening is filled with a contact plug.