Interactive band diagrams of an n-channel MOSFET showing how a negative body-to-source bias moves the inversion point from 2 phi F to 2 phi F minus V BS.

Substrate doping NA
Body bias VBS
Surface potential φS
Into the substrate along the dashed cut Conduction band along the surface
φF
Inversion point 2φF − VBS
ns / NA
Surface state
Surface electron density vs φS (gray: VBS = 0, blue: current VBS)