a piezoelectric substrate grinding step of grinding a lower surface of the piezoelectric substrate, the lower surface being opposite to {HEAD ~ an upper surface} on which the ejection grooves and {TAIL ~ the non ejection grooves} are formed, to allow the non ejection grooves to penetrate the piezoelectric substrate from the upper surface through the lower surface thereof 
a piezoelectric substrate grinding step of grinding a lower surface of the piezoelectric substrate , the lower surface being opposite to { HEAD ~ an upper surface } on which the ejection grooves and { TAIL ~ the non ejection grooves } are formed , to allow the non ejection grooves to penetrate the piezoelectric substrate from the upper surface through the lower surface thereof
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