The present disclosure relates to a semiconductor structure. The semiconductor structure includes a semiconductor-on-insulator (SOI) substrate having a bottom substrate, a buried oxide layer disposed on the bottom substrate, and a semiconductor layer disposed on the buried oxide layer. The semiconductor structure further includes a doped layer embedded in the semiconductor layer and above the buried oxide layer, and a contact structure extending into the semiconductor layer from the top surface of the semiconductor layer. The contact structure is electrically connected to the doped layer.