Analytical model and characterization of small-geometry buried-channel depletion MOSFETs

Small-geometry buried-channel depletion MOSFETs (BCD-MOSFETs) are characterized based on an analytical model that includes short-channel, narrow-channel, and carrier-velocity saturation effects. The drain current is calculated based on the surface electrons induced by the gate-bias voltage and the buried-channel junction FET. The narrow-channel effect is modeled not only by the additional depletion-layer charges created by a fringing-field effect in the field region, but also by the effective channel width as a function of gate-bias voltage. Surface-electron mobility is modeled as a function of the vertical and lateral electrical fields created by the gate-bias and drain voltages, while bulk-electron mobility is described as a function of the lateral electric field due to the drain voltage. Theoretical results on drain current are in good agreement with experimental results.