| 摘要 |
PURPOSE:To protect an integrated circuit from operational errors by a method wherein an N-type region connected to a prescribed terminal of an integrated circuit is surrounded by a P-type region and the P-type region is surrounded by an N-type region so that it may be isolated from a P-type substrate. CONSTITUTION:An N-type region 11 is surrounded for isolation by a P-type region composed of a P-type buried region 6 and P-type isolating region 9. The P-type region is surrounded by an N-type region composed of an N-type buried region 5 and N-type epitaxial region 8. That is, a P-type region composed of a P-type substrate 1, P-type buried region 7, and P-type isolating region 10 is electrically isolated from other elements in an integrated circuit. Accordingly, upon application of a negative potential to a terminal 3 under abnormal conditions, an N-P-N transistor wherein the N-type region 11 is the emitter, the P-type region 6 is the base, and an N-type region 5 is the collector, starts functioning. The terminal 3 is clamped at a potential level which is lower by a P-N junction forward threshold voltage than the ground potential, and absorbs excess surges. Under the circumstances, an integrated circuit connected to the terminal 3 is protected and a current is drawn out of a ground terminal only. In this way, the integrated circuit is protected from erroneous operations. |
