A two-dimensional etching simulator named ESPRIT (FOOTNOTE: ESPRIT--Etching Simulation PRogram with an Improved sTring model.) has been developed to simulate LSI patterning. The etching simulator includes isotropic and anisotropic components. Its calculation method is based on the string model. ESPRIT can simulate etched profiles for multilayers with different etching rates and calculate side etching using sloped incidental anisotropic components. In addition, location correction, loop elimination, point insertion, and point elimination are provided for stable and accurate calculations. Simulated profiles coincide well with those from experiments in terms of relationship between the groove width and etched depth. ESPRIT can support to design LSI patterning process.