Semiconductor device packages include a redistribution layer (RDL) with carbon-based conductive elements. The carbon-based material of the RDL may have low electrical resistivity and may be thin (e.g., less than about 0.2 μm). Adjacent passivation material may also be thin (e.g., less than about 0.2 μm). Methods for forming the semiconductor device packages include forming the carbon-based material (e.g., at high temperatures (e.g., at least about 550° C.)) on an initial support wafer with a sacrificial substrate. Later or separately, components of a device region of the package may be formed and then joined to the initial support wafer before the sacrificial substrate is removed to leave the carbon-based material joined to the device region.