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US 6,191,455 B1Granted
Semi-conductor device protected by electrostatic protection device from electrostatic discharge damage
AssigneeNEC Corporation
InventorAkira Shida
Life of this patent
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Abstract
A semiconductor device has electrostatic protection device capable of preventing characteristic fluctuation of MOS transistor caused by electrostatic discharge. PN junction is formed in between N+ cathode region and boron upward diffusion region of P+ substrate, thus being formed low breakdown voltage diode whose breakdown occurs at low reverse voltage. The diode is in use as electrostatic protection device of either input circuit or output circuit so that it is capable of protecting internal device transistor efficiently from applied surge when gate oxide film becomes thin film.
Claims5
A semiconductor device comprising:
- a MOS transistor formed on a first conductivity type semiconductor layer, said layer being formed on a high density semiconductor substrate, which is of said first conductivity type, through an impurity upward diffusion region by an epitaxial growth;
- and
- a diode, which is an electrostatic protection device, connected between either a gate electrode of said MOS transistor, or a drain region of said MOS transistor, and said high density semiconductor substrate, wherein an impurity density of an anode side at a junction of said diode is higher than an impurity density of an anode side at a drain junction of said MOS transistor, but lower than an impurity density of the high density semiconductor layer.
Dependencies are inferred from the claim text.