Protection circuit utilizing distributed transistors and resistors

Claim 1

A semiconductor device provided with a protection circuit, the semiconductor device comprising: a semiconductor substrate of one conductivity type; a field effect transistor formed in said semiconductor substrate, said field effect transistor having a source and a drain formed in said semiconductor substrate and a gate formed on said semiconductor substrate between said source and said drain via an insulating film; a first terminal formed on said semiconductor substrate for connecting with an external circuit; a first region of the other conductivity type formed in said semiconductor substrate, said first region having a first and a second end portion and an elongated intermediate portion extending between said first and second end portions; first means for connecting said first terminal with said first end portion of said first region; second means for connecting said second end portion of said first region with said gate of said field effect transistor; a second region of said other conductivity type formed in said semiconductor substrate, said second region having an elongated portion extending parallel to said intermediate portion of said first region with a distance therebetween determined such that said elongated portion of said second region and said intermediate portion of said first region operate as a distributed bipolar lateral transistor together with a portion of said semiconductor substrate located therebetween, said second region further having a contact portion at one end of said elongated portion, said elongated portion having no direct electrical connection thereto; a second terminal formed on said semiconductor substrate for receiving a reference voltage; and third means for connecting said contact portion of said second region with said second terminal.