Insulator for integrated circuit and its manufacture

PROBLEM TO BE SOLVED: To obtain insulator having low permitivity and gap filling capability, by annealing a curing flowable oxide layer in an atmosphere of hydrogen and aluminum, diffusing hydrogen in the flowable oxide layer, and specifying the permittivity. SOLUTION: This insulator is used for covering interconnection wiring level 3 in the semiconductor substrate surface containing a semiconductor device, provided with a first flowable oxide layer 1 for covering the interconnection wiring level 3, and cures the oxide layer 1. The flowable oxide layer 1 is annealed in an atmosphere of hydrogen and aluminum. Hydrogen is diffused in the flowable oxide layer 1, and its permitivity is reduced to be less than 3.2. As the flowable oxide layer 1, cured hydrogensilsesquioxane is contained. Thereby special insulator having comparatively low permitivity less than 3.2 and excellent gap filling capability can be obtained.