Method of process integration for high voltage and mixed signal technologies

A kind of method for integrating process of high voltage device and mixed signal device is disclosed in the present invention. The invention contains the followings: providing a semiconductor substrate; defining the well region on the semiconductor substrate; using field oxide to define the active region; forming gate oxide on the active region; forming the first polysilicon at the active region and on the field oxide; depositing capacitive dielectric material on the first polysilicon of the field oxide; depositing the second polysilicon on the capacitive dielectric material to form the capacitor; performing double diffusion drain (DDD) implantation to form source/drain region of high voltage device; conducting lightly doped drain (LDD) implantation to form lightly doped drain region; forming the spacer; and performing source/drain implantation.