Silicon-controlled rectifier electrostatic discharge protection device and method for forming the same

A method for forming an SCR ESD device, comprising:

• providing a semiconductor substrate;
• forming, in the semiconductor substrate, a P-type well region and an N-type well region adjacent to the P-type well region;
• forming a second center-doped region that extends across the P-type well region and the N-type well region;
• forming a first center-doped region in and enclosed by the second center-doped region, a depth of the second center-doped region being greater than a depth of the first center-doped region, wherein the first center-doped region and the second center-doped region are doped with impurity ions of a same type, a concentration of the impurity ions in the first center-doped region being higher than a concentration of the impurity ions in the second center-doped region;
• forming a first P-type doped region in the P-type well region at a first side of the second center-doped region;
• forming a first N-type doped region in the P-type well region at the first side of the second center-doped region, the first N-type doped region being located between the first P-type doped region and the second center-doped region;
• forming a second N-type doped region in the N-type well region at a second side of the second center-doped region;
• and
• forming a second P-type doped region in the N-type well region at the second side of the second center-doped region, the second P-type doped region being located between the second N-type doped region and the second center-doped region.