ELECTROSTATIC BREAKDOWN PROTECTIVE ELEMENT OF SEMICONDUCTOR INTEGRATED CIRCUIT

摘要

PURPOSE:To increase gate breakdown pressure resistance and current driving capability of a transister by a method wherein a source-side diffusion layer is also formed under an element dielectric isolation film, and a gate electrode overlaps with at least the source only on an element separation insulating film, in an electrostatic breakdown protective element by a transistor of MOS type in which an element dielectric isolation film is used for a gate insulating film. CONSTITUTION:An electrostatic breakdown protective element F3 of a transistor of MOS type in which an element dielectric isolation film 7 is used for a gate insulating film comprises a P-type Si substrate 3, drains 1, 4 formed by using an N--well opposite in conductivity type to the P-type Si substrate, sources 2, 5 formed by using an N--well similar to that described above, a gate electrode 6 of polycrystalline Si, and a LOCOS film 7 which is a gate insulating film. The sources 2, 5 and the drains 1, 4 overlap with the gate electrode 6 under the LOCOS film 7. Furthermore, since the gate 6 and the drains 1, 4 are electrically connected to terminal D, and the sources 2, 5 are electrically connected to ground E, if a positive static charges are applied to the terminal, the gate voltage increases, causing the transistor to be turned on and causing static charges to escape to the ground.