solve the aforementioned problem of the prior art, and an object thereof is to provide a method of producing a semiconductor device that prevents voids from being formed in the trench isolation structure.
A method of producing a semiconductor device according to the present invention includes the following steps. A first film having a dielectric property, a second film having an oxidation property different from that of the first film, and a layer serving as a mask material are successively formed on a semiconductor substrate. A mask pattern for forming a trench in the semiconductor substrate is formed by performing an etching treatment on the first film, the second film, and the layer serving as a mask material. A trench is formed by performing an etching treatment on thesemiconductor substrate using the mask pattern as a mask. An etching treatment is performed so that a position of a side surface of the second film exposed on a side surface of the mask pattern will be retreated from a position of a side surface of the first film. An oxide film is formed on a surface of the first film and the trench including the retreated side surface of the second film by performing a thermal treatment. A buried dielectric film is formed on the oxide film so as to fill the trench. In the retreating step of retreating the position of the side surface of the second film from the position of the side surface of the first film, the side surface of the second film