The short-channel properties of multi-gate SOI MOSFETs (MuGFETs) are studied by numerical simulation. The evolution of characteristics such as DIBL, subthreshold slope, and threshold voltage roll-off is analyzed as a function of channel length, silicon film or fin thickness, gate dielectric thickness and dielectric constant, and as a function of the radius of curvature of the corners. The notion of an equivalent gate number is introduced. This number ranges from 2 for a double-gate device to 4 in a gate-all-around transistor. The equivalent gate number can be used in general equations to predict the absence or presence of short-channel effects. As a general rule, increasing the equivalent gate number improves the short-channel behavior of the devices. Similarly, increasing the radius of curvature of the corners improves the control of the channel region by the gate. (c) 2006 Elsevier Ltd. All rights reserved.