Two-dimensional diffusion of aluminum implanted through a mask in silicon has been measured after furnace or rapid thermal annealings. Chemical staining on cross-sectioned samples was used to determine both the vertical and the lateral junction depths. The spreading resistance standard procedure was adopted to measure the vertical profiles while a new procedure was developed for the determination of the lateral diffusion profiles. The difference in the measured profile by staining and spreading resistance is related to the spilling phenomenon that distorts the carrier concentration profile on beveled samples. Moreover, experimentally aluminum diffusion parameters and segregation coefficient at the Si/SiO2 interface have been introduced in advanced one-dimensional (SUPREM III) and two-dimensional (SUPREM IV) process simulators. The good agreement between the simulated and the experimental data, for both the lateral and the vertical directions, indicates that these process simulators can reproduce with accuracy the aluminum diffusion.