Under radio-frequency operation of MOSFETs, not only conventional 1-V characteristics and their derivatives but also higher-order phenomena have to be modeled accurately for reliable circuit performance prediction. To reproduce such critical device characteristics model development tends to follow device physics as much as possible. The surface-potential distribution, which is the origin of all device features, is the key modeling quantity and leads to straightforward description accurate even for higher-order phenomena. This is demonstrated with the circuit simulation model HiSIM for the cases of noise modeling, small-signal analysis as well as large-signal analysis.