A PHYSICAL CHARGE-BASED MODEL FOR NON-FULLY DEPLETED SOI MOSFETS AND ITS USE IN ASSESSING FLOATING-BODY EFFECTS IN SOI CMOS CIRCUITS

A new model for the non-fully depleted (NFD) SOI MOSFET is developed a nd used to study floating-body effects in SOI CMOS circuits. The charg e-based model is physical, yet compact and thus suitable for device/ci rcuit simulation. Verified by numerical device simulations and test-de vice measurements, and implemented in (SOI)SPICE, it reliably predicts floating-body effects resulting from free-carrier charging in the NFD /SOI MOSFET, including the purportedly beneficial supra-ideal subthres hold slope due to impact ionization and a saturation current enhanceme nt due to thermal generation. SOISPICE CMOS circuit simulations reveal that the former effect is not beneficial and could be detrimental, bu t the latter effect can be beneficial, especially in low-voltage appli cations, when accompanied by a dynamic floating-body effect that effec tively reduces static power. The dynamic floating-body effects are hys teretic, however, and hence exploitation of the beneficial ones will n ecessitate device/circuit design scrutiny aided by physical models suc h as the one presented herein.