As devices are scaled to characteristic sizes of one-tenth-micron and below, special care must be taken to insure these devices are modeled appropriately. The underlying physics in such small devices can have a profound effect on device behavior and performance, yet modeling tools developed for past device generations rarely possess the required physical basis to correctly predict device behavior at these small dimensions. This problem is well recognized by many research groups world-wide.

As a result, research activities to improve the physical basis of device simulation programs divide into three approaches:

• extensions to present "drift-diffusion" analyses, by adding additional equations governing carrier momentum and energy. Such modeling is often referred to as "energy-transport" or "hydrodynamic" device modeling.
• solutions based upon the Boltzmann Transport Equation, often incorporating detailed descriptions of semiconductor properties such as band structure and scattering rates.
• full quantum-mechanical treatments, emphasizing the wave-like nature and interference properties of carriers at these small dimensions.

In 1987, a project was undertaken to create a device modeling computer program that would contain the necessary physics but allow modeling of a broad class of "realistic" device structures. The result is a program called DAMOCLES, which is mnemonic for Device Analysis Using Monte Carlo et Poisson solver. This program combines a self-consistent solution, via a Monte Carlo sampling technique, to the Boltzmann transport equation (BTE) and the Poisson equation. Conditionally, the Schrödinger equation (see the details provided by the Computational Electronics Group, University of Illinois, Urbana-Champaign) can also be coupled into the self-consistent solution, which allows DAMOCLES to model quantization in inversion layers and quantum wells. DAMOCLES uses the full band structure of the semiconductor with consistently calculated scattering rates in pursuit of physical accuracy and rigor. DAMOCLES solves the BTE in three wavevector-space dimensions, and the Poisson equation in two real-space dimensions. Adding time as a final state variable, DAMOCLES conducts a six-dimensional calculation. The program is computationally intensive, but delivers a wealth of detailed information about the internal behavior of a semiconductor device. Today, after 16 man-years of development, the DAMOCLES program represents the state-of-the-art in this type of device simulation program. DAMOCLES was written by M.V. Fischetti and S.E. Laux.