QUANTUM-MECHANICAL EFFECTS ON THE THRESHOLD VOLTAGE OF ULTRATHIN-SOI NMOSFETS

This paper describes theoretically the dependence of the threshold voltage, V(TH), of SOI MOSFET's on a wide range of top silicon layer thickness, t(s), by using both classical and quantum-mechanical methods. The quantum-mechanical effects become remarkable below the critical thickness and rase V(TH) with decreasing t(s). The classical method cannot be applied in such a thin t(s) region, since classically obtained V(TH) decreases monotonously with decreasing t(s) even below the critical thickness. As a result, the V(TH) curve as a function of t(s) can be divided into two regions with a boundary of a critical t(s), and the classical method can be suitably applied above that critical thickness.