The technology for manufacturing integrated circuits involves several basic physical and chemical processes: lithography, etching, deposition, etc. This is what we call the 'wafer foudry'. These processes are carried out on silicon wafers in a tightly controlled environment called 'clean rooms'. For each circuit there is a corresponding set of masks generated by CAD tools and drawn by design teams.
At the end of the wafer manufacturing phase, each chip is assembled in a package and tested before it is incorporated into its final application.