A semiconductor structure and a method for manufacturing the same are provided. The method comprises following steps. A first silicon-containing conductive material is formed on a substrate. A second silicon-containing conductive material is formed on the first silicon-containing conductive material. The first silicon-containing conductive material and the second silicon-containing conductive material have different dopant conditions. The first silicon-containing conductive material and the second silicon-containing conductive material are thermally oxidized for turning the first silicon-containing conductive material wholly into an insulating oxide structure, and the second silicon-containing conductive material into a silicon-containing conductive structure and an insulating oxide layer.