Patent ID: 7190006

Claim:
A three-layer diac including: a substrate of a first conductivity type with a high doping level, a lightly-doped epitaxial layer of a second conductivity type including, in a vicinity of the substrate, a more heavily-doped portion, a heavily-doped region of the first conductivity type on an upper surface side of the epitaxial layer, a region of the second conductivity type more heavily doped than the epitaxial layer under the region of the first conductivity type and that does not extend beyond said heavily-doped region of the first conductivity type, a channel stop ring of the second conductivity type more heavily doped than the epitaxial layer, outside of the said heavily-doped region of the first conductivity type, and a wall of the first conductivity type outside of said ring, joining the substrate; wherein the region of the second conductivity type is directly above the more heavily-doped portion of the lightly-doped epitaxial layer.