A proximity effect correction system has been developed by utilizing an efficient dose modulation technique based on a double Gaussian proximity function. A shaped electron beam system is assumed to be used. Two improvements are made. First, an optimal exposure dose on each pattern is determined by a new fast iterative method. The optimal dose makes the development isocontour conform to the pattern specification fairly well. Second, a ‘‘simple cell unit algorithm’’ that one of identical cells is proximity‐corrected, and the result is used to the other remaining cells is introduced. This offers to both decrease the processing time and save the memory/disk space. The present system is applied to the data processing of scaled‐down version of an aluminum wiring layer pattern of 16 Mbit dynamic random access memory with its minimum dimension of 0.4 μm. The calculation is successfully completed within 1 h of CPU time on a 10 MIPS general‐purpose computer. The dimensional accuracy of 10% is confirmed experimentally for the pattern including minimum features of 0.4 μm in the combination of trilayer resist process.