Abstract: A biochip includes a substrate, an insulating layer, a semiconductor layer, a dielectric layer, a metal layer, and a protective layer. The semiconductor layer is disposed on the insulating layer and has a reaction region. The dielectric layer is disposed on the semiconductor layer and has a first opening. The metal layer is disposed on the dielectric layer and includes a source, a drain, and a wall structure. The wall structure surrounds the first opening, the source, and the drain. The protective layer is disposed on the metal layer and has a flat part, a protruding part, a second opening, and a third opening. The flat part surrounds and defines the second opening. The protruding part is disposed corresponding to the wall structure, and the protruding part surrounds and defines the third opening. The second opening connects the third opening and the first opening to expose the reaction region.