| 摘要 |
PURPOSE:To improve the circuit characteristics of a semiconductor device by forming the second oxidized film which reaches an insulating substrate on the region exposed with silicon pattern and the third oxidized film which reaches at least the first oxidized film and does not reach the substrate, thereby eliminating the floating state of the substrate while corresponding to the trend to the decrease in the thickness of a silicon layer. CONSTITUTION:Though the thickness of a silicon layer formed on a sapphire substrate 31 is extremely thin, e.g., 4,000Angstrom , a p<+> type impurity layer 40 having sufficient thickness to become wirings between the third oxidized film 39 and the substrate 31 can remain. Accordingly, a semiconductor base 45 between a source region 43 and a drain region 44 can be externally led through the layer 40 and the base leading region 46, and the potential can be fixed. Thus, the circuit characteristics can be improved. Further, since the third oxidized film 39 on the layer 40 to become wirings is thick, the floating capacity between the wirings and the silicon layer can be reduced, and the circuit characteristics such as propagation velocity and the like does not deteriorate. |
