Patent ID: 9202908
Filing Date: 2015-12-01
Classification: H01L

Abstract:
1. A protection diode comprising: a semiconductor substrate; a gate side well region of a first conductivity type in the semiconductor substrate; a grounding side well region of the first conductivity type in the semiconductor substrate and, wherein the gate side well region is located within the grounding side well region; a gate side diffusion region of a second conductivity type in the semiconductor substrate and located within the gate side well region; a grounding side diffusion region of the second conductivity type in the semiconductor substrate, separated from the gate side diffusion region by parts of the gate side well region and the grounding side well region, and surrounding and joined to the grounding side well region; a gate side electrode connected between a gate of a transistor protected by the protection diode and the gate side diffusion region; and a grounding electrode connected to the grounding side diffusion region, wherein dopant impurity concentration in the grounding side well region is lower than dopant impurity concentration in the gate side well region, whereby breakdown voltage of the protection diode differs depending upon polarity of a surge voltage applied between the gate side electrode and the grounding side electrode.