Hot-carrier effects in body-tied fin-type field effect transistors (FinFETs) are investigated. As the gate bias increases, coupling effects of two gates facing each other suppress the lateral channel electric field more effectively at double gate metal oxide FETs (MOSFETs) than at single gate MOSFETs. In double gate FinFETs, this effect is even further enhanced when the fin width is narrowed. The Substrate current produced by an impact ionization process becomes large as fin width increases. In the generalized substrate Current model, the maximum substrate current bias condition is approximately V-G/V-D similar to 0.5. However, in the double-gate FinFETs, it was (V-G - V-T)/V-D similar to 0.3. There are two competing stress conditions: the maximum substrate current condition, and the maximum gate current condition. Device degradation is compared for various fin widths after both type of stress. It was found that the maximum substrate current stress condition degraded the device more significantly. The narrow fin is more immune to both stress biases than the wide fin. Thus, the narrow fin is appropriate for further device scaling and reliability. The supply voltage which corresponds to a 10-years lifetime was 1.31 V for the worst hot-carrier stress case.