Printhead having layered heater elements and electrodes

1. A printhead comprising:

a plurality of nozzles;

a plurality of heaters having heater elements and electrodes, the electrodes connecting current from a power source to the heater elements to heat, and form gas bubbles in, liquid within the nozzles which causes ejection of the liquid from the nozzles,

wherein the heaters are formed of layers of a single material, a first layer of the single material having portions of different thickness respectively defining the heater elements and electrodes, and a second layer of the single material overlaying and spaced from the first layer having a single thickness defining the electrodes.

2. A printhead according to claim 1 wherein the single material is titanium nitride.

3. A printhead according to claim 1 wherein, in the first layer, the thickness of the single material defining the electrodes is greater than the thickness of the single material defining the heater elements.

4. A printhead according to claim 1 comprising a substrate having a substrate surface, the areal density of the nozzles relative to the substrate surface exceeding 10,000 nozzles per square cm of substrate surface.

5. A printhead according to claim 1 comprising a structure that is formed by chemical vapor deposition, the nozzles being incorporated in the structure.

6. A printhead according to claim 1 comprising a structure which is less than 10 microns thick, the nozzles being incorporated in the structure.