This paper investigates the silicon film thickness influence on extensionless Ultra Thin Body and Buried Oxide (UTBB) FDSOI devices applied in a dynamic threshold voltage (DT2) operation (VB=VG) over the conventional one (VB=0V). A 6nm silicon thickness in enhanced DT (eDT), where the back gate bias is a multiple value of the front gate one (VB=k×VG), was also considered and compared to the other configurations and to a 14nm silicon film. The better coupling of a thinner silicon film leads to superior DC parameters like lower subthreshold swing and DIBL, while the thicker device presents a higher gmmax and lower GIDL. Regarding the eDT performance, the parameters of the thinner channel vary less than for the thicker one.