Trench-Based NLDMOS with Stress-Enhanced Electron Mobility in the Channel and Drift Region

In this paper, a novel CESL (SiN cap layer) strained NLDMOS with a trench-based stress modulation structure is studied by numerical simulation. A compressive CESL, instead of a tensile one which is often used in a conventional strained NLDMOS, is taken as the stressor. In common sense, though the compressive CESL will stretch the drift region, it will also squeeze the channel and hence suppress the electron mobility there. But this is not the case for our device for that the trench-based structure will alter the channel stress from compressive to tensile. Thus, the tensile stress is realized in the channel and drift regions simultaneously, whereas this can not happen in a conventional strained NLDMOS for its drift region is always compressively strained by the tensile CESL adopted. With the stress-enhanced electron mobility in gate and drift regions, the output performance of the device is substantially boosted. As another benefit, the application of a compressive CESL facilitates the integration of the strained NLDMOS with the strained PMOS in one integrated circuit.