3.7.3 Effective Oxide Thickness / Effective Capacitance

If $QMTCENCV_i = 0$, then $C_{ox}/C_{ox,acc}$ (with $EOT/EOTACC$) will continue to be used for both I-V and C-V. Else the following calculations yield a $C_{ox,eff}$ that shall be used for C-V purposes. However $C_{ox}$ will continue to be used for I-V. For calculation of $C_{ox,eff}$, the physical oxide thickness, $TOXP$ scaled appropriately will be added to the inversion charge centroid, $T_{cen}$ calculated above instead of using $EOT$.

If $QMTCENCV_i \ne 0$,

$C_{ox,eff} = \begin{cases} \dfrac{3.9 \cdot \epsilon_0}{\Bigg[ TOXP \cdot \dfrac{3.9}{EPSROX} + T_{cen} \cdot \dfrac{QMTCENCV_i}{\epsilon_{ratio}} \Bigg]} &\text{if } GEOMOD \ne 3 \\ \\ \dfrac{3.9 \cdot \epsilon_0}{R \cdot \Bigg[ \dfrac{1}{\epsilon_{ratio}} \cdot ln \Bigg( \dfrac{R}{R - T_{cen}} \Bigg) + \dfrac{3.9}{EPSROX} \cdot ln \Bigg( 1 + \dfrac{T_{oxp}}{R} \Bigg) \Bigg]} &\text{if } GEOMOD = 3 \end{cases}$

$(3.336)$