Protective circuit on insulating substrate for protecting MOS integrated circuit

In a protective circuit for a MOS integrated circuit comprising a MOS IC body including at least one MOS transistor at an input stage of a MOS integrated circuit, the at least one input stage transistor being made of an island-like semiconductor layer formed on an insulating substrate and having source, drain and gate electrodes;

• and
• the improvement wherein the protective circuit is formed on the insulating substrate of the MOS IC body for protecting the MOS integrated circuit, the protective circuit comprising:
• an R-C protective circuit connected between a signal input terminal and a gate electrode of the at least one MOS input stage transistor and comprising a protective MOS transistor made of a first region of an island-like semiconductor layer of one conductivity type on an insulating substrate and having source, drain and gate electrodes, said protective MOS transistor being connected between ground and the gate electrode of the at least one MOS input stage transistor, the source electrode of said protective MOS transistor being connected to ground and the drain electrode of said protective MOS transistor being connected to the gate electrode of the at least one MOS input stage transistor;
• a sinuous resistor being formed on an insulating layer on a second region of the island-like semiconductor layer which is connected to ground, overlying the insulating substrate so as to provide a stray capacitance and connected between the signal input terminl and the gate electrode of the protective MOS transistor, said resistor having a conductivity type opposite to said one conductivity type of the island-like semiconductor layer;
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• a bonding pad formed on the insulating layer on the second region of the semiconductor layer overlying the insulating substrate, said bonding pad being connected to one end of the resistor so as to provide a stray capacitance between said semiconductor layer and said bonding pad, said stray capacitances forming the capacitive component of said R-C protective circuit.