| 摘要 |
In a manufacturing process of an SOI structure semiconductor device in which an MOS capacitor is located on an SOI substrate, the capacitor insulating film of the MOS capacitor is prevented from degrading due to a bimetal effect, which is caused by a thermal treatment and characteristic to the SOI substrate. A trench is formed to surround the MOS capacitor in the SOI substrate, thick oxide films are formed on sidewalls defining the trench, and the trench is filled with polysilicon to complete a trench isolation layer. Because the thick oxide films have a coefficient of thermal expansion that is different from that of a silicon semiconductor layer of the SOI substrate, the thick oxide films are able to prevent the capacitor insulating film from degrading in film quality due to the thermal treatment in the manufacturing process. As a result, an SOI semiconductor device in which an MOS capacitor on an SOI substrate offers performance comparable to an MOS capacitor on a silicon substrate can be formed.
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