A new phase shift lithography method has been developed that allows different integrated circuit features to be focused on different optical planes that conform to the wafer surface topography. In principle, each pattern in the circuit has its own unique focal plane. The direction and magnitude of each focus shift is determined by the design of the shifter patterns. This method is applicable for use with conventional opaque mask patterns and unattenuated phase shift patterns. The characteristics of this multiple-focus-plane technique have been evaluated experimentally and confirmed theoretically through mathematical modeling using TCC optical imaging theory. Experiments were conducted using i-line positive resist processes for different phase-shift patterns. This paper discusses the effects of changes in phase shift and recommends practical mask design approaches.