| 摘要 |
PURPOSE:To enable the formation of a protection diode at an arbitrary position of a MOSFET substrate by a method wherein a polycrystalline Si layer having a loop PN junction is formed independently from a polycrystalline Si gate of MOSFET and a source electrode thereof in a back-to-back protection diode wherein a polycrystalline Si layer is used. CONSTITUTION:A polycrystalline Si layer which becomes a MOSFET protection diode is formed on an insulation film 6. This polycrystalline Si layer is composed of a P type diffusion Si layer 7 formed in a loop and of N<+> type diffusion layers 7c and 7b adjacent to the layer 7a inside and outside the same via a PN junction. The polycrystalline Si layer 7 which becomes the protection diode is formed on the insulation film 6 in the same process with that for forming a mesh-shaped polycrystalline Si gate of MOSFET, separately from the latter. Among the polycrystalline Si layers, the N<+> type diffusion layer 7b located inside is connected to the gate of MOSFET via an Al wiring 8', while the N<+> type diffusion Si layer 7c outside is connected to a source electrode via an Al wiring 8. |
