Dielectric spectroscopy measurements were performed on planar silicon nanostructures buried within a crystalline Si that form a nanoscale Si-layered system. An insight into the specific behavior of the free-carrier population confined in the surface potential well was then made possible. It was found that the presence or the absence of the SiO2 passivation modifies considerably relaxation responses of the studied structures. A clear differentiation of two dielectric responses: from the same sample with and without electronic passivation allowed determination of the conduction behavior in the surface c-Si delimited by the nanoscale Si-layered system. The sample with a 100 nm thick SiO2 layer (and an excellent quality of the SiO2/c-Si interface) exhibits a fractional power-law dielectric response, corresponding clearly to the generalized Mittag-Leffler pattern. Simultaneously, the dielectric response of a bare sample (after the total RIE of the previously deposited SiO2 layer, about 10 nm native SiO2 layer and poor quality of the SiO2/c-Si interface) is dominated by the conductivity term. (C) 2014 Elsevier B.V. All rights reserved.