Patent ID: 7417287

Claim:
An electrostatic discharge device having a controllable trigger voltage, said electrostatic discharge device comprising: a P-type substrate; an N-type well, formed inside said P-type substrate; a first N+-type region, formed inside said P-type substrate and outside said N-type well; a first P+-type region, formed inside said P-type substrate and outside said N-type well, wherein said first P+-type region is isolated from said first N+-type region by a first field oxide; a second N+-type region, formed inside said N-type well; a second P+-type region, formed inside said N-type well; a third N+-type region, formed between said second P+-type region and a second field oxide, wherein said second N+-tyne region is next to said second P+-tvpe region and said second P+-type region is next to said third N+-tvpe region. said third N+-type region is isolated from any conductor and is isolated from said first N+-type region by said second field oxide, and a junction between said second field oxide and said third N+-type region is spaced from an edge of said N-type well by a predetermined distance; a first electrode, electrically connected to said first P+-type region and said first N+-type region through a first conductor; and a second electrode, electrically connected to said second P+-type region and said second N+-type region through a second conductor; wherein said controllable trigger voltage is determined by adjusting said predetermined distance which allows said edge of said N-type well to be located in a range between said second field oxide and said third N+-type region.