An electronic component element includes a piezoelectric substrate and a comb-shaped electrode located on one principal surface of the piezoelectric substrate. A support layer is arranged around the comb-shaped electrode. A cover layer is disposed so as to cover the support layer and the comb-shaped electrode. Via-hole electrodes extend through the cover layer and are connected to the comb-shaped electrode. An uneven portion is located on a principal surface of the cover layer that is opposite to a principal surface of the cover layer that is opposed to the comb-shaped electrode.