. . . "As in the above, the nitride film 32 is formed at about 700??? C. Since, however, gas including oxygen held in the interlayer insulating films 16 and 20 is already removed by the annealing in the process of FIG. 1C, there is almost no degassing of gas including oxygen from the interlayer insulating films 16 and 20 in the formation process of the nitride film 32." . .