The impact of different gate dielectrics on the low-frequency (LF) noise behavior is investigated in UTBOX SOI nMOSFETs. Hafnium silicate (HfSiO) devices are compared to silicon dioxide (SiO2) ones in terms of low-frequency noise apart from the analysis of both front and back-channels. Despite the improvement of process steps for obtaining good dielectric layers, high-k devices have shown elevated current noise spectral density due to the higher number of traps which also degrades the front-channel mobility. Although the buried oxide (BOX) of both wafers is formed by thermal SiO2, the strong electrostatic coupling between front and back-channels has resulted in a worse noise performance for high-k devices even at the back interface.