Abstract: A method for forming a metal plug is provided. The method is used to form a metal plug without a hole on a glue/barrier layer within a trench when the glue/barrier layer has been formed for a while. A substrate with a trench therein and a glue/barrier layer formed conformal to the profile of the substrate is provided. A post-treatment is performed on the glue/barrier layer to prevent moisture absorption and to make the glue/barrier become dense. The post-treatment comprises a plasma treatment or a deep UV plus laser treatment. After performing the post-treatment step, a metal layer is formed on the glue/barrier layer at least to fill in the trench. The metal layer other than that filling the trench is removed to form a metal plug.

Abstract: A method for forming a shallow trench isolation structure. A pad oxide layer is formed over a substrate. A hard mask layer is formed over the pad oxide layer. A portion of the hard mask layer, the pad oxide layer and the substrate is removed to form a trench in the substrate. Insulation material is deposited into the trench to form an insulation plug. The hard mask layer is removed to expose the sidewalls of the insulation plug. Spacers are formed on the exposed sidewalls of the insulation plug. Ions are implanted into the substrate. The pad oxide layer, the spacers and a portion of the insulation plug are removed. Finally, a gate oxide layer thicker in region around the edge of the insulation plug is formed over the substrate by oxidation.