Solid state sensors having timing capabilities below 50 ps RMS are becoming a mandatory requirement in particle tracking techniques of future experiments at colliders. Within this context, silicon sensors with 3D structure provide an interesting solution, due to their intrinsic fast response and radiation resistance. The performance of such devices is strictly dependent on the geometric structure of the electrodes and can be considerably optimised by design using suitable tools to accurately model the sensor behaviour. This paper illustrates the development, performance and use of the TCoDe simulator, specifically dedicated to the fast simulation of carrier transportation phenomena in solid state sensors. Some examples of its effectiveness in the design and analysis of 3D sensors are also given.