MOSFET SiO₂ Gate Oxide Capacitance Calculator
Compute ideal SiO₂ gate oxide capacitance per unit area from thickness using Cox = εox/tox and εox = 3.9·ε0.
Description
Calculate ideal SiO₂ gate oxide capacitance per unit area in fF/µm² from oxide thickness in nanometers.
This calculator models the gate dielectric as a uniform parallel plate of SiO₂ with relative permittivity 3.9. It returns oxide capacitance per unit area, often written Cox, rather than total gate capacitance.
When to use MOSFET SiO₂ Gate Oxide Capacitance Calculator
- Convert an SiO₂ process thickness into Cox for compact calculations
- Check fF/µm² and F/cm² unit conversions
- Supply oxide capacitance to a first-order inversion-charge estimate
How the calculation works
Cox equals oxide permittivity divided by oxide thickness. After calculation in F/cm², the result is converted with 1 F/cm² = 10⁷ fF/µm².1
Cox = εox / tox, where εox = 3.9·ε0 Interpreting the result
Cox increases inversely with thickness: halving an ideal SiO₂ thickness doubles its capacitance per area.
Assumptions and limitations
- The model omits interface states, depletion, quantum capacitance, leakage, fringing, and process nonuniformity.
- The fixed permittivity is specific to SiO₂; high-k dielectrics require their own permittivity or an equivalent oxide thickness interpretation.
- Multiply by gate area separately if total ideal oxide capacitance is needed.
References
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EE105 Lecture 7: MOSFET — University of California, Berkeley