A transient voltage suppressor is provided, comprising a heavily doped substrate connected to a first node, a first doped layer formed on the heavily doped substrate, a second doped layer formed on the first doped layer, a first heavily doped region and a second heavily doped region formed in the second doped layer and coupled to a second node, and a plurality of trenches arranged in the heavily doped substrate, having a depth not less than that of the first doped layer for electrical isolation. The heavily doped substrate, the second doped layer, and the second heavily doped region belong to a first conductivity type. The first doped layer and the first heavily doped region belong to a second conductivity type. By employing the proposed present invention, pn junctions of the transient voltage suppressor can be controlled beneath the surface, thereby reducing the junction capacitance effectively.