Silicon controlled rectifier structure with improved punch through resistance

A silicon controlled rectifier comprising:

• a semiconductor region having:
• a buried layer having a first conductivity type and a dopant concentration;
• a first region having a second conductivity type and a dopant concentration;
• a second region of the first conductivity type that contacts the buried layer and the first region, the second region having a dopant concentration that is less than the dopant concentration of the buried layer;
• a third region of the second conductivity type that contacts the second region, the third region contacting the top surface of the second region;
• a fourth region of the first conductivity type that contacts the second region, the fourth region contacting the top surface of the second region and being spaced apart from the third region;
• a first conductive region that contacts the third region;
• and
• a second conductive region that contacts the third region, the second conductive region being spaced apart from the first conductive region.

A silicon controlled rectifier comprising:

• a first semiconductor region of a first conductivity type, the first semiconductor region having a dopant concentration;
• a buried region of the first conductivity type, the buried region contacting the first semiconductor region and having a dopant concentration that is greater than the dopant concentration of the first semiconductor region;
• a second semiconductor region of a second conductivity type that contacts the first semiconductor region, the second semiconductor region being spaced apart from the buried region, the second semiconductor region including all contiguous regions of the second conductivity type;
• and
• a third semiconductor region of the first conductivity type that contacts the first semiconductor region, the third semiconductor region being spaced apart from the buried region and the second semiconductor region, and having a dopant concentration that is greater than the dopant concentration of the first semiconductor region.

A silicon controlled rectifier comprising:

• a first semiconductor region of a first conductivity type, the first semiconductor region having a dopant concentration;
• a buried region of the first conductivity type, the buried region contacting the first semiconductor region and having a dopant concentration that is greater than the dopant concentration of the first semiconductor region;
• a second semiconductor region of a second conductivity type that contacts the first semiconductor region, the second semiconductor region being spaced apart from the buried region, the second semiconductor region including all contiguous regions of the second conductivity type;
• a third semiconductor region of the first conductivity type that contacts the first semiconductor region, the third semiconductor region being spaced apart from the buried region and the second semiconductor region, and having a dopant concentration that is greater than the dopant concentration of the first semiconductor region;
• and
• a fourth semiconductor region of the second conductivity type that contacts the first semiconductor region, the buried region, and the third semiconductor region.