PURPOSE: To completely eliminate a crack to be generate at a nitride film and to prevent aluminum from being externally diffused by forming to add a silicon film further on a second oxide film, and so disposing component materials disposed on and under the nitride film in a symmetrical way to the film.

CONSTITUTION: Aluminum ions 2 are first implanted to a silicon board 1. Then, the first oxide film 3 is formed on the surface of the board 1. This is because a buffer film is provided between a nitride film 4 formed in next step and the board 1. Then, the film 4 is formed, for example, by a plasma CVD method. Thereafter, the second oxide film 5 is formed on the film 4. Further, a silicon film 6 is formed on the film 5 by sputtering. The film 6 is provided to completely eliminate the crack of the film 4 due to the incomplete prevention of the crack generated at the film 4 when a high temperature heat treatment is executed, because that films disposed above and below the film 4 in a symmetrical way to the center in a wiring structure is optimum.