Modular bipolar-CMOS-DMOS analog integrated circuit and power transistor technology

1. A CMOS arrangement of transistors formed in a semiconductor substrate, said substrate being doped with P-type impurity and not comprising an epitaxial layer, said CMOS arrangement comprising a first CMOS pair, said first CMOS pair comprising a first PMOS and a first NMOS, and a second CMOS pair, said second CMOS pair comprising a second PMOS and a second NMOS:

said first PMOS comprising:

a first N well having a relatively deep central portion and relatively shallow side portions, said side portions of said first N well underlying a field oxide layer, said central portion of said first N well underlying a first opening in said field oxide layer;

a first gate overlying a channel region of said first N well and separated from said substrate by a first gate oxide layer;

a first P-type source region located at the surface of said substrate on one side of said first gate; and

a first P-type drain region located at the surface of said substrate on an opposite said of said first gate from said first P-type source region;

said first NMOS comprising:

a first P well having a relatively deep central portion and relatively shallow side portions, said side portions of said first P well underlying the field oxide layer, said central portion of said first P well underlying a second opening in said field oxide layer;

a second gate overlying a channel region of said first P well and separated from said substrate by a second gate oxide layer;

a first N-type source region located at the surface of said substrate on one side of said second gate; and

a first N-type drain region located at the surface of said substrate on an opposite said of said second gate from said first N-type source region;

said second PMOS comprising:

a second N well having a relatively deep central portion and relatively shallow side portions, said side portions of said second N well underlying the field oxide layer, said central portion of said second N well underlying a third opening in said field oxide layer;

a third gate overlying a channel region of said second N well and separated from said substrate by a third gate oxide layer;

a second P-type source region located at the surface of said substrate on one side of said third gate; and

a second P-type drain region located at the surface of said substrate on an opposite said of said third gate from said second P-type source region; and

said second NMOS comprising:

a second P well having a relatively deep central portion and relatively shallow side portions, said side portions of said second P well underlying the field oxide layer, said central portion of said second P well underlying a fourth opening in said field oxide layer;

a fourth gate overlying a channel region of said second P well and separated from said substrate by a fourth gate oxide layer;

a second N-type source region located at the surface of said substrate on one side of said fourth gate; and

a second N-type drain region located at the surface of said substrate on an opposite said of said fourth gate from said second N-type source region;

wherein said second P-type drain region is separated by a first offset distance from said third gate and said channel region underlying said third gate and said first P-type drain region is separated by a second offset distance from said first gate and said channel region underlying said first gate, said first offset distance being greater than said second offset distance;

wherein said second N-type drain region is separated by a third offset distance from said fourth gate and said channel region underlying said fourth gate and said first N-type drain region is separated by a fourth offset distance from said second gate and said channel region underlying said second gate, said third offset distance being greater than said fourth offset distance; and

wherein said second N well comprises an implanted N layer, said N layer comprising a deep section in said central portion of said second N well, shallow sections in said side portions of said second N well, and transition sections connecting said deep section and said shallow sections of said N layer, said implanted N layer having a doping concentration greater than a doping concentration of a remaining portion of said second N well.

2. A CMOS arrangement of transistors formed in a semiconductor substrate, said substrate being doped with P-type impurity and not comprising an epitaxial layer, said CMOS arrangement comprising a first CMOS pair, said first CMOS pair comprising a first PMOS and a first NMOS, and a second CMOS pair, said second CMOS pair comprising a second PMOS and a second NMOS:

said first PMOS comprising:

a first N well having a relatively deep central portion and relatively shallow side portions, said side portions of said first N well underlying a field oxide layer, said central portion of said first N well underlying a first opening in said field oxide layer;

a first gate overlying a channel region of said first N well and separated from said substrate by a first gate oxide layer;

a first P-type source region located at the surface of said substrate on one side of said first gate; and

a first P-type drain region located at the surface of said substrate on an opposite said of said first gate from said first P-type source region;

said first NMOS comprising:

a first P well having a relatively deep central portion and relatively shallow side portions, said side portions of said first P well underlying the field oxide layer, said central portion of said first P well underlying a second opening in said field oxide layer;

a second gate overlying a channel region of said first P well and separated from said substrate by a second gate oxide layer;

a first N-type source region located at the surface of said substrate on one side of said second gate; and

a first N-type drain region located at the surface of said substrate on an opposite said of said second gate from said first N-type source region;

said second PMOS comprising:

a second N well having a relatively deep central portion and relatively shallow side portions, said side portions of said second N well underlying the field oxide layer, said central portion of said second N well underlying a third opening in said field oxide layer;

a third gate overlying a channel region of said second N well and separated from said substrate by a third gate oxide layer;

a second P-type source region located at the surface of said substrate on one side of said third gate; and

a second P-type drain region located at the surface of said substrate on an opposite said of said third gate from said second P-type source region; and

said second NMOS comprising:

a second P well having a relatively deep central portion and relatively shallow side portions, said side portions of said second P well underlying the field oxide layer, said central portion of said second P well underlying a fourth opening in said field oxide layer;

a fourth gate overlying a channel region of said second P well and separated from said substrate by a fourth gate oxide layer;

a second N-type source region located at the surface of said substrate on one side of said fourth gate; and

a second N-type drain region located at the surface of said substrate on an opposite said of said fourth gate from said second N-type source region;

wherein said second P-type drain region is separated by a first offset distance from said third gate and said channel region underlying said third gate and said first P-type drain region is separated by a second offset distance from said first gate and said channel region underlying said first gate, said first offset distance being greater than said second offset distance; and

wherein said second N-type drain region is separated by a third offset distance from said fourth gate and said channel region underlying said fourth gate and said first N-type drain region is separated by a fourth offset distance from said second gate and said channel region underlying said second gate, said third offset distance being greater than said fourth offset distance;

said arrangement further comprising a relatively heavily doped N-type guard ring in said side portions of said second N well, said N-type guard ring surrounding said central portion of said second N well.

3. The CMOS arrangement of claim 2 wherein said N-type guard ring is located beneath said field oxide layer and is spaced apart from said third opening in said field oxide layer.

4. A CMOS arrangement of transistors formed in a semiconductor substrate, said substrate being doped with P-type impurity and not comprising an epitaxial layer, said CMOS arrangement comprising a first CMOS pair, said first CMOS pair comprising a first PMOS and a first NMOS, and a second CMOS pair, said second CMOS pair comprising a second PMOS and a second NMOS:

said first PMOS comprising:

a first N well having a relatively deep central portion and relatively shallow side portions, said side portions of said first N well underlying a field oxide layer, said central portion of said first N well underlying a first opening in said field oxide layer;

a first gate overlying a channel region of said first N well and separated from said substrate by a first gate oxide layer;

a first P-type source region located at the surface of said substrate on one side of said first gate; and

a first P-type drain region located at the surface of said substrate on an opposite said of said first gate from said first P-type source region;

said first NMOS comprising:

a first P well having a relatively deep central portion and relatively shallow side portions, said side portions of said first P well underlying the field oxide layer, said central portion of said first P well underlying a second opening in said field oxide layer;

a second gate overlying a channel region of said first P well and separated from said substrate by a second gate oxide layer;

a first N-type source region located at the surface of said substrate on one side of said second gate; and

a first N-type drain region located at the surface of said substrate on an opposite said of said second gate from said first N-type source region;

said second PMOS comprising:

a second N well having a relatively deep central portion and relatively shallow side portions, said side portions of said second N well underlying the field oxide layer, said central portion of said second N well underlying a third opening in said field oxide layer;

a third gate overlying a channel region of said second N well and separated from said substrate by a third gate oxide layer;

a second P-type source region located at the surface of said substrate on one side of said third gate; and

a second P-type drain region located at the surface of said substrate on an opposite said of said third gate from said second P-type source region; and

said second NMOS comprising:

a second P well having a relatively deep central portion and relatively shallow side portions, said side portions of said second P well underlying the field oxide layer, said central portion of said second P well underlying a fourth opening in said field oxide layer;

a fourth gate overlying a channel region of said second P well and separated from said substrate by a fourth gate oxide layer;

a second N-type source region located at the surface of said substrate on one side of said fourth gate; and

a second N-type drain region located at the surface of said substrate on an opposite said of said fourth gate from said second N-type source region;

wherein said second P-type drain region is separated by a first offset distance from said third gate and said channel region underlying said third gate and said first P-type drain region is separated by a second offset distance from said first gate and said channel region underlying said first gate, said first offset distance being greater than said second offset distance; and

wherein said second N-type drain region is separated by a third offset distance from said fourth gate and said channel region underlying said fourth gate and said first N-type drain region is separated by a fourth offset distance from said second gate and said channel region underlying said second gate, said third offset distance being greater than said fourth offset distance;

said arrangement further comprising an N-type isolation layer underlying said first and second P wells and at least a portion of at least one of said first and second N wells, said N-type isolation layer and said at least one of said first and second N wells together forming an isolation structure that isolates said first P well and second P well from said P-type substrate.

5. The CMOS arrangement of claim 4 wherein said first and second N well together form an annular structure that laterally surrounds said first P well and said second P well.

6. The CMOS arrangement of claim 5 wherein said first and second N wells vertically overlap said N-type isolation layer.

7. The CMOS arrangement of claim 4 wherein a doping concentration profile taken at a vertical cross-section through said central portion of said first P well comprises a series of two or more vertically separated P-type Gaussian profiles.

8. The CMOS arrangement of claim 4 wherein one of said first and second N wells laterally surrounds said first P well and the other of said first and second N wells laterally surrounds said second P well.

9. The CMOS arrangement of claim 8 wherein said first and second N wells vertically overlap said N-type isolation layer so as to isolate said first P well and said second P well from each other and from said substrate.

10. The CMOS arrangement of claim 4 wherein a doping concentration profile taken at a vertical cross-section through said central portion of said second P well comprises a series of two or more vertically separated P-type Gaussian profiles.