Semidonductor device and method of manufacturing the same

Claim 1

A semiconductor device comprising: a semiconductor substrate (1); an emitter region (30) of a first conductivity type formed on said semiconductor substrate (1); a base region (24) of a second conductivity type formed to surround said emitter region (30); a low impurity concentration collector region (4, 6) of the first conductivity type formed to surround said base region (24); a high impurity concentration collector region (2) of the first conductivity type formed under said low impurity concentration collector region (4, 6); and a well region (5) of the second conductivity type formed in contact with said low impurity concentration collector region (4, 6); characterized in that at least part of said low impurity concentration collector region (4, 6) which lies between said emitter region (30) and said high impurity concentration collector region (2) is formed to have an impurity concentration lower than that of at least part of said low impurity concentration collector region (4, 6) which lies between said base region (24) and said well region (5) of the second conductivity type.

Claim 10

A method of manufacturing a semiconductor device, comprising the steps of: forming at least two first buried layers (2) having a high impurity concentration on selected surfaces in a second MOS transistor-forming region and a bipolar transistor-forming region of said semiconductor substrate (1), respectively, and forming a second buried layer (3) having a high impurity concentration in a first MOS transistor-forming region of said semiconduc­tor substrate (1); forming an epitaxial layer (4) of a first conduc­tivity type on the entire surfaces of said semiconductor substrate (1); forming a well region (5) of a second conductivity type in said first MOS transistor-forming region, said well region (5) having an impurity concentration higher than that of said epitaxial layer (4); forming simultaneously at least two regions (40, 8) of said first conductivity type in that portion of said epitaxial layer (4) which is located above said second MOS transistor-forming region and ion-injected regions (8) in which said device-isolation insulating film (7) is to be formed, said ion-injected regions preventing said field region from being inverted, and that portion of said epitaxial layer (4) which is located above said bipolar transistor-forming region and other than that portion located below a base-forming portion (40), respectively; forming device-isolation insulating film (7) on selected surfaces of the resultant structure; forming a first MOS transistor in said well region (5) of the second conductivity type formed in said first MOS transistor-forming region, and a second MOS transis­tor in said well region (6) of the first conductivity type formed in said second MOS transistor-forming region; and forming a bipolar transistor in said epitaxial layer (4) and said well region (6) of the first conduc­tivity type formed in said bipolar transistor-forming region.

Claim 11

A method of manufacturing a semiconductor device, comprising the steps of: forming at least two first buried layers (2) having a high impurity concentration on selected surfaces in a second MOS transistor-forming region and a bipolar transistor-forming region of said semiconductor substrate (1), respectively, and forming a second buried layer (3) having a high impurity concentration in a first MOS transistor-forming region of said semiconduc­tor substrate (1); forming an epitaxial layer (4) of a first conduc­tivity type on the entire surfaces of said semiconductor substrate (1); forming a well region (5) of a second conductivity type in said first MOS transistor-forming region, said well region (5) having an impurity concentration higher than that of said epitaxial layer (4); forming simultaneously at least two regions (40, 8) of said first conductivity type in that portion of said epitaxial layer (4) which is located above said second MOS transistor-forming region and ion-injected regions (8) in which said device-isolation insulating film (7) is to be formed, said ion-injected regions preventing said field region from being inverted, and that portion of said epitaxial layer (4) which is located above said bipolar transistor-forming region and other than that portion located below a base-forming portion (40), respectively; forming device-isolation insulating film (7) on selected surfaces of the resultant structure; forming a first MOS transistor in said well region (5) of the second conductivity type formed in said first MOS transistor-forming region, and a second MOS transis­tor in said well region (6) of the first conductivity type formed in said second MOS transistor-forming region; and forming a bipolar transistor in said epitaxial layer (4) and said well region (6) of the first conduc­tivity type formed in said bipolar transistor-forming region.

Claim 15

A method of manufacturing a semiconductor device, characterized by comprising the steps of: forming at least two first buried layers (2) having a high impurity concentration on selected surfaces in a second MOS transistor-forming region and a bipolar transistor-forming region of said semiconductor substrate (1) respectively and forming a second buried layer (3) having a high impurity concentration in a first MOS transistor-forming region of said semiconduc­tor substrate (1); forming an epitaxial layer (4) of a first conduc­tivity type on the entire surfaces of said semiconductor substrate (1); forming a well region (5) of a second conductivity type in said first MOS transistor-forming region, said well region (5) having an impurity concentration higher than that of said epitaxial layer (4); forming a field region (40) of the first conductiv­ity type in the surface of said epitaxial layer (4) which surrounds a base region (24) of said bipolar transistor-forming region; forming device-isolation insulating films (7) on selected surfaces of the resultant structure; forming a first MOS transistor in said well region (5) of the second conductivity type formed in said first MOS transistor-forming region, and a second MOS transis­tor in said well region (6) of the first conductivity type formed in said second MOS transistor-forming region; and forming a bipolar transistor in said epitaxial layer (4) and said well region (6) of the first conduc­tivity type formed in said bipolar transistor-forming region.

Claim 16

A method of manufacturing a semiconductor device, characterized by comprising the steps of: forming at least two first buried layers (2) having a high impurity concentration on selected surfaces in a second MOS transistor-forming region and a bipolar transistor-forming region of said semiconductor substrate (1) respectively and forming a second buried layer (3) having a high impurity concentration in a first MOS transistor-forming region of said semiconduc­tor substrate (1); forming an epitaxial layer (4) of a first conduc­tivity type on the entire surfaces of said semiconductor substrate (1); forming a well region (5) of a second conductivity type in said first MOS transistor-forming region, said well region (5) having an impurity concentration higher than that of said epitaxial layer (4); forming a field region (40) of the first conductiv­ity type in the surface of said epitaxial layer (4) which surrounds a base region (24) of said bipolar transistor-forming region; forming device-isolation insulating films (7) on selected surfaces of the resultant structure; forming a first MOS transistor in said well region (5) of the second conductivity type formed in said first MOS transistor-forming region, and a second MOS transis­tor in said well region (6) of the first conductivity type formed in said second MOS transistor-forming region; and forming a bipolar transistor in said epitaxial layer (4) and said well region (6) of the first conduc­tivity type formed in said bipolar transistor-forming region.