The Sn method for solving the Spencer-Lewis equation for electron transport has been extended to treat three-dimensional multiregion problems. The flux continuity condition, which holds when the flux is expressed as a function of path length for single material region problems, is generalized for multiregion problems by reexpressing the flux as a function of energy. Expressing the fluxes in terms of fixed energy increments, independent of material, rather than fixed path length increments, results in a set of Sn/diamond-difference equations that are nearly identical in form to conventional Sn/diamond-difference equations. The Sn method is then applied to calculate electron energy deposition due to 200-keV electron beams incident on problem geometries typical of silicon and gallium-arsenide semiconductor microelectronic devices. The energy deposition results were found to compare well with results of ACCEPT Monte Carlo calculations. Computer run times required for the Sn calculations were found to be lower than that required for Monte Carlo by factors ranging from 30 to 50.