The invention provides a low-capacity TVS (
Transient Voltage Suppressor) tube and a preparation method thereof. The low-capacity TVS tube is provided with a P-type substrate provided with a groove, and a first N + layer and a first N-layer which are sequentially arranged on the groove; wherein two sides of the first N + layer perpendicular to the epitaxial growth direction are provided with first isolation
dielectric layers, two sides of the first N-layer perpendicular to the epitaxial growth direction are provided with second isolation
dielectric layers, one side, far away from the first N + layer, of the first N-layer is doped with P-type ions, and a first region, doped with the P-type ions, in the first N-layer is connected with an
electrode. The grooves are etched by using a relatively large depth-to-
width ratio, so that the risks of difficulty in digging deep grooves and insufficient filling of isolation
dielectric layers are avoided, the process difficulty is greatly reduced, meanwhile, isolation is performed in advance by using the isolation dielectric layers, isolation failure caused by the problems of
diffusion, alignment and the like is avoided, in addition, the width of the PN junction can be flexibly adjusted according to design requirements, and the manufacturing cost is reduced. And therefore, the surge capacity can be improved, and the
capacitance can also be reduced.