A transient voltage suppressor includes a substrate, a first well, a second well, a first electrode, a second electrode, a doped region and a heavily-doped region. The first well is formed in the substrate and near a surface of substrate. The second well is formed in the first well and near the surface. The first electrode and second electrode are formed in the second well and near the surface respectively. The first well and first electrode have a first electrical property. The second well and second electrode have a second electrical property. The doped region is formed between the first electrode and second electrode and near the surface and electrically connected with the first well and second well. The heavily-doped region is formed under the doped region. The heavily-doped region has the same electrical property with the doped region and has higher doping concentration than the doped region.