| 摘要 |
To prevent cracks in an insulator buried in a trench and fill the insulator completely in a place to be filled up. A process comprises: forming a trench 1 a extending to an embedded insulation film 3 at a determined position on a first silicon substrate 1 of an SOI substrate 10 ; forming a first BPSG film 6 on the first silicon substrate 1 including the trench 1 a not to fill in the trench 1 a completely; forming an NSG film 7 on the first BPSG film 6 , and forming a second BPSG film 8 on the NSG film 7 . Each film forming step is performed in the same CVD furnace by a CVD method and a process changeover from one step to next is completed by changing a condition of gas species supplied into the CVD furnace.
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