What is TCAD, anyway?

TCAD stands for Technology Computer Aided Design, which is not that self-explanatory. What it really refers to is computer programs able to simulate either the workings of a semiconductor device (device simulation) or the fabrication process of a semiconductor device (process simulation).
Often the result of a process simulation, which is called a "mesh" or "grid" is fed into a device simulator to evaluate the performance or the behavior of the device that has been "virtually fabricated".
Simulations are very inexpensive and fast compared to actual prototype fabrication. They are also an excellent tool to understand semiconductor physics.