After being treated with clean wafer, about 1 μm thick thermal oxidation films 13a, {TAIL ~ 13b} are formed on the bonding surfaces of these substrates by, for example, {HEAD ~ thermal oxidation} or CVD in a clean atmosphere of below Class 1 as shown in FIG 3A 
After being treated with clean wafer , about 1 μm thick thermal oxidation films 13a , { TAIL ~ 13b } are formed on the bonding surfaces of these substrates by , for example , { HEAD ~ thermal oxidation } or CVD in a clean atmosphere of below Class 1 as shown in FIG 3A
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