A triac has a vertical structure formed from a silicon substrate having an upper surface side. A main metallization on the upper surface side has a first portion resting on a first region of a first conductivity type formed in a layer of a second conductivity type. A second portion of the main metallization rests on a portion of the layer. A gate metallization on the upper surface side rests on a second region of the first conductivity type formed in the layer in the vicinity of the first region. A porous silicon bar formed in the layer at the upper surface side has a first end in contact with the gate metallization and a second end in contact with the main metallization.