Thyristor and method for the same

A thyristor, comprising:

• a base region, with a first side and a second side opposite to the first side;
• a pair of first doping regions, formed on the first side and the second side respectively, and in contact with the base region;
• at least a second doping region, formed between one of the first doping regions and the base region, wherein the second doping region is in contact with the base region and the first doping region;
• at least a third doping region, formed inside one of the first doping regions, and in contact with the first doping region, wherein the third doping region is not in contact with the base region, wherein the doping type of the first doping regions is different from the doping type of the second doping region, the third doping region, and the base region;
• and
• a pair of metal layers, in contact with the first doping regions respectively, wherein the first doping regions and the third doping region are all located between the metal layers, and one of the metal layers is further in contact with the third doping region, but not in contact with the second doping region.