A semiconductor structure is used for releasing an electrostatic discharge current and comprises a substrate, a first buried layer, a second buried layer, a first well, a second well, a first doped region, a trench gate and a second doped region. The first and second buried layers are formed on the substrate. The first well is formed over the first buried layer. The second well is formed over the second buried layer and overlaps a part of the second buried layer. The first doped region is formed in the first well. The trench gate extends into the second well and the first buried layer. The second doped region is formed in the second well and contacts the trench gate.