Method of fabricating a twin tub CMOS device

Claim 1

A method of fabricating a semiconductor device on a semiconductor substrate having a wafer layer thereon containing a dopant, said method comprising the steps of: forming an oxide layer on a major surface of said wafer layer; forming on the exposed surface of said oxide layer a layer of nitride material having a window exposing said oxide layer; forming a first mask layer at least over a first portion of said window; introducing a first type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said first mask layer to thereby form a first region of predetermined depth in said wafer layer; removing said first mask layer; forming a second mask layer at least over a second portion of said window substantially adjacent to said first portion of said window; introducing a second type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said second mask layer to thereby form a second region of predetermined depth in said wafer layer; removing said second mask layer; and exposing said wafer layer to a relatively elevated temperature to thereby simultaneously drive said first type of dopant and said second type of dopant deeper into said wafer layer; whereby substantially adjacent wells of opposite dopant type are obtained in said semiconductor substrate.

Claim 2

A method of fabricating a semiconductor device on a semiconductor substrate having a wafer layer thereon containing a dopant, said method comprising the steps of: forming an oxide layer on a major surface of said wafer layer; forming on the exposed surface of said oxide layer a layer of nitride material having a window exposing said oxide layer; forming a first mask layer at least over a first portion of said window; introducing a first type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said first mask layer to thereby form a first region of predetermined depth in said wafer layer; removing said first mask layer; forming a second mask layer at least over a second portion of said window substantially adjacent to said first portion of said window; introducing a second type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said second mask layer to thereby form a second region of predetermined depth in said wafer layer; removing said second mask layer; and exposing said wafer layer to a relatively elevated temperature to thereby simultaneously drive said first type of dopant and said second type of dopant deeper into said wafer layer; whereby substantially adjacent wells of opposite dopant type are obtained in said semiconductor substrate.

Claim 6

A method of fabricating a semiconductor device on a semiconductor substrate having a wafer layer thereon containing a dopant, said method comprising the steps of; forming a first oxide layer on a major surface of said wafer layer; forming on the exposed surface of said first oxide layer a layer of nitride material having a first window exposing said first oxide layer; forming a first mask layer at least over a first portion of said first window; introducing a first type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said first mask layer to thereby form a first region of predetermined depth in said wafer layer; removing said first mask layer; forming a second mask layer at least over a second portion of said first window substantially adjacent to said first portion of said first window; introducing a second type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said second mask layer to thereby form a second region of predetermined depth in said wafer layer; removing said second mask layer and at least a portion of said first oxide layer to open a second window, said second window extending between the walls of said first window to expose a portion of said major surface therebetween; and exposing said wafer layer to a relatively elevated temperature to thereby simultaneously drive said first type of dopant and said second type of dopant deeper into said wafer layer; whereby substantially adjacent wells of opposite dopant type are obtained in said semiconductor substrate.

Claim 7

A method of fabricating a semiconductor device on a semiconductor substrate having a wafer layer thereon containing a dopant, said method comprising the steps of; forming a first oxide layer on a major surface of said wafer layer; forming on the exposed surface of said first oxide layer a layer of nitride material having a first window exposing said first oxide layer; forming a first mask layer at least over a first portion of said first window; introducing a first type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said first mask layer to thereby form a first region of predetermined depth in said wafer layer; removing said first mask layer; forming a second mask layer at least over a second portion of said first window substantially adjacent to said first portion of said first window; introducing a second type of dopant through the regions of said oxide layer and said nitride layer which do not underlie said second mask layer to thereby form a second region of predetermined depth in said wafer layer; removing said second mask layer and at least a portion of said first oxide layer to open a second window, said second window extending between the walls of said first window to expose a portion of said major surface therebetween; and exposing said wafer layer to a relatively elevated temperature to thereby simultaneously drive said first type of dopant and said second type of dopant deeper into said wafer layer; whereby substantially adjacent wells of opposite dopant type are obtained in said semiconductor substrate.