METHOD FOR MANUFACTURING WELLS OF SEMICONDUCTOR DEVICES

摘要

PURPOSE: A well fabrication method of CMOS transistor is provided to increase a margin of design rule by using triple wells and independent operating a well-bias each other. CONSTITUTION: The method comprises the steps of forming an isolating oxide(12) in a semiconductor substrate(10) of a first conductive type; forming an isolating well(14) of a second conductive type in the semiconductor substrate(10); and forming an N-well(18) and a P-well(22) on the surface of the isolating well(14), thereby forming triple wells which can independently operated. The N and P-wells(18,22) are formed by diffusion wells or retrograded wells.