The application of an unconditionally stable locally one-dimensional finite-difference time-domain (LOD-FDTD) method for the full-wave simulation of semiconductor devices is described. The model consists of the electron equations for semiconductor devices in conjunction with Maxwell??s equations for electromagnetic effects. Therefore the behaviour of an active device at high frequencies is described by considering the distributed effects, propagation delays, electron transmit time, parasitic elements and discontinuity effects. The LOD-FDTD method allows a larger Courant??Friedrich??Lewy number (CFLN) as long as the dispersion error remains in the acceptable range. Hence, it can lead to a significant time reduction in the very time consuming full-wave simulation. Numerical results show the efficiency of the presented approach.