| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of punch-through while restraining enhancement in a parasitic capacitance in a silicon-on-insulator(SOI) semiconductor device. SOLUTION: This semiconductor device comprises a substrate 4, a buried insulting film 3, and a first conductive type of semiconductor layer 1b. Two impurity regions of second conductive type 7 are formed with a channel forming region 1c between, with a distance from each other in the semiconductor layer 1b. The buried insulating film 2 comprises a first region 2a including the lower region of the channel forming region 1c and a second region 2b which has the specific inductive capacity which is lower than that of the first region 2a and includes the lower region of at least one of the two impurity regions 7. In order to make this difference in the specific inductive capacity, an element to lower the specific inductive capacity (i.e., fluorine) may be added to the second region 3b and also an element to raise it (i.e., nitrogen, carbon) may be added to the first region 2a.
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