The passivation quality at the interface between dielectric interlayer (IL) stacks and liquid-phase crystallized silicon (LPC-Si) was investigated by means of high-frequency capacitance-voltage (C-V) measurements. The developed device structure was based on a molybdenum layer sandwiched between the glass substrate and the IL/LPC-Si stack. C-V curves were discussed in terms of hysteresis formation and capacitance relaxation. We varied the nitrogen and hydrogen content in the a-SiO x N y :H layer adjacent to the LPC-Si and studied the effects on the defect state density at the IL/LPC-Si interface (D it ) as well as on the effective charge density in the IL (Q IL,eff ). Both parameters are crucial for the analysis of chemical and field-effect passivation. Furthermore, the effect of an additional hydrogen plasma treatment (HPT) on D it and Q IL,eff was investigated. A Gaussian-like defect distribution at around 0.1 eV above the mid gap energy is significantly reduced by the additional HPT. With additional HPT, the lowest D it and highest Q IL,eff at mid gap, i.e., D it ¼ (3.5 AE 0.7) Â 10 11 eV À1 cm À2 and Q IL,eff ¼ (1.6 AE 0.3) Â 10 12 cm
À2, correspond to the passivation by an a-SiO x N y :H layer with a low nitrogen and high hydrogen content.