Quantum Mechanical Effects on the Threshold Voltage of Double-Gate Metal–Oxide–Semiconductor Field-Effect Transistors

概要

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A model for a metal–oxide–semiconductor field-effect transistor (MOSFET) with a double gate (DG) is developed. Quantum mechanical effects on the threshold voltage ($V_{\text{TH}}$) are modeled and investigated analytically. The analytic model shows how $V_{\text{TH}}$ is increased with quantum mechanical effect. The model is applicable to both symmetric DG (SDG) and asymmetric DG (ADG) nMOSFETs, and is also applicable to both doped and undoped DG nMOSFETs. The analytic results are verified by comparing with the results obtained from simulations using Schred, and good agreement is observed. The $V_{\text{TH}}$ of an ADG nMOSFET will shift more than that of an SDG nMOSFET, and the $V_{\text{TH}}$ of a DG transistor with (110)-silicon (Si) orientation will shift more than that of a DG transistor with (100)-Si orientation. When the silicon thickness $t_{\text{si}} < 3$ nm, the $V_{\text{TH}}$ shift will be significant, and one should be careful in the use of an extremely thin silicon body. When the body doping density ($N_{\text{A}}$) is not high (${<}10^{18}$ cm-3), the $V_{\text{TH}}$ shift is almost the same for different $N_{\text{A}}$. When $N_{\text{A}} > 10^{18}$ cm-3, the higher the $N_{\text{A}}$, the more the $V_{\text{TH}}$ shift.
2010-03-25