The invention discloses a semiconductor structure. The semiconductor structure comprises a substrate with a first conduction type, a deep well with a second conduction type, a first well with the first conduction type, a second well with the second conduction type, a grid electrode, a first insulator and a second insulator, wherein the deep well is formed inside the substrate and extends downwards from the surface of the substrate; the first well and the second well extend downwards from the surface of the substrate to be formed in the deep well; the first well is separated from the first well; the grid electrode is formed on the substrate and arranged between the first well and the second well; the first insulator extends downwards from the surface of the substrate and is formed between the grid electrode and the second well; the second insulator extends downwards from the surface of the substrate and is adjoined with the first well; the ratio of the depth of the first insulator to the depth of the second insulator is less than 1.