Piezoelectric device and its manufacturing method

A piezoelectric device comprising:

• a substrate;
• a lower electrode layer formed on the substrate;
• a piezoelectricity layer formed on the lower electrode layer;
• an upper electrode layer formed on the piezoelectricity layer;
• and
• at least one of a lower adhesion layer formed between the piezoelectricity layer and the lower electrode layer so as to abut on the piezoelectricity layer and the lower electrode layer or an upper adhesion layer formed between the piezoelectricity layer and the upper electrode layer so as to abut on the piezoelectricity layer and the upper electrode layer;
• wherein a portion of the upper adhesion layer and the lower adhesion layer, which abuts on the piezoelectricity layer, is made of tungsten in which an α phase and a β phase coexist, a ratio of tungsten of β phase is reduced as going away from the piezoelectricity layer, and a portion which abuts on the upper electrode layer or the lower electrode layer is made of α-phase tungsten.

A piezoelectric device comprising:

• a substrate;
• a lower electrode layer formed on the substrate;
• a piezoelectricity layer formed on the lower electrode layer;
• an upper electrode layer formed on the piezoelectricity layer;
• and
• at least one of a lower adhesion layer formed between the piezoelectricity layer and the lower electrode layer so as to abut on the piezoelectricity layer and the lower electrode layer or an upper adhesion layer formed between the piezoelectricity layer and the upper electrode layer so as to abut on the piezoelectricity layer and the upper electrode layer;
• wherein the upper adhesion layer and the lower adhesion layer are configured by the transition of β-phase tungsten formed without heating the substrate into α-phase tungsten.