| 摘要 |
PURPOSE:To reduce high-frequency impedance by a method wherein an insulating film is thinner under a power source wiring different in potential from a substrate and the conductivity type of a diffusion layer located under the power source wiring is same as that of the substrate for an increase in the capacity distributed between the power source wiring and substrate. CONSTITUTION:In a device composed of a P-type substrate 1, N-type diffusion layer 2, P-type diffusion layer 3, insulating film 4 of silicon dioxide or the like, ground wiring 5, power source wiring 6, signal wiring 7, and protecting film 8, the insulating film 4 is thinner under the power source wiring 6 than under the signal wiring 7. Further, the conductivity type of the N-type diffusion layer 2 under the signal wiring 7 is different from that of the P-type substrate 1, and the conductivity type of P-type diffusion layer 3 under the source wiring 6 is same as that of the P-type substrate 1. Generally speaking, capacity per unit area is inversely proportional to the thickness of an insulating film sandwiched between electrodes. It follows therefore that the capacity per unit area the power source wiring 6 produces with the P-type substrate 1 is larger than the capacity per unit area the signal wiring 7 produces with the P-type substrate 1.
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