A display may have a color filter layer and a thin-film transistor layer. A layer of liquid crystal material may be located between the color filter layer and the thin-film transistor (TFT) layer. The TFT layer may include thin-film transistors formed on top of a glass substrate. A passivation layer may be formed on the thin-film transistor layers. A first low-k dielectric layer may be formed on the passivation layer. Data line routing structures may be formed on the first low-k dielectric layer. A second low-k dielectric layer may be formed on the first low-k dielectric layer. A common voltage electrode and associated storage capacitance may be formed on the second low-k dielectric layer. The first and second low-k dielectric, layers may be formed from material having substantially similar refractive indices to maximize backlight transmittance and may have appropriate thicknesses so as to minimize parasitic capacitive loading.