To achieve high conversion efficiencies, advanced silicon solar cell architectures such as interdigitated back contact solar cells demand that defects at both the n(+) and p(+) doped Si surfaces are passivated simultaneously by a single passivation scheme. In this work, corona charging experiments show that the fixed charge density Q(f) is a key parameter governing the passivation of both surface types. Alternatively, Q(f) can be controlled from strongly negative to even positive values by carefully tuning the SiO2 interlayer thickness in SiO2/Al2O3 stacks prepared by atomic layer deposition (ALD). This control in Q(f) allows for a superior passivation of n(+) Si surfaces by SiO2/Al2O3 stacks compared to a single layer Al2O3. For instance, for SiO2 interlayer thicknesses of similar to 3-14 nm, the recombination parameter of an n(+) Si surface having a high surface doping concentration N-s of 2 x 10(20) cm(-3) was reduced from J(On+)=81 fA/cm(2) to J(On+)=50 fA/cm(2). Simulations predict that the SiO2/Al2O3 stacks outperform Al2O3 passivation layers particularly on n+ Si surfaces having a moderate N-s in the range of 10(18)-10(20) cm(-3). On p(+) Si surfaces, J(Op+) <= 54 fA/cm(2) was achieved for all ALD SiO2 interlayer thicknesses investigated (i.e., 1-14 nm). The SiO2/Al2O3 stacks presented in this work are compatible with SiNx capping and subsequent high-temperature firing steps, which are typically used in solar cell processing. Furthermore, the results were successfully reproduced in an industrial ALD batch reactor using a low-temperature process. This makes ALD SiO2/Al2O3 stacks a promising candidate for the simultaneous passivation of n(+) and p(+) Si surfaces in solar cells. (C) 2015 Elsevier B.V. All rights reserved.