Piezoelectric thin film resonant element and circuit component using the same

A piezoelectric thin film resonant element comprising a resonant portion having a laminate structure including:

• a piezoelectric film having a predetermined plan-view shape;
• a lower electrode formed on a lower surface of the piezoelectric film and having an outer circumference including an inclined portion which is inclined with respect to a surface of the film at a predetermined angle;
• and an upper electrode formed on an upper surface of the piezoelectric film;
• wherein the resonant portion has a greater acoustic impedance at a part of the laminate structure corresponding to the inclined portion of the lower electrode than a part of the laminate structure inner than the inclined portion of the lower electrode.

A piezoelectric thin film resonant element comprising:

• a resonant portion having a laminate structure including:
• a piezoelectric film having a predetermined plan-view shape;
• a lower electrode formed on a lower surface of the piezoelectric film and having an outer circumference including an inclined portion which is inclined with respect to a surface of the film at a predetermined angle;
• and an upper electrode formed on an upper surface of the piezoelectric film;
• and
• an additional film formed on the upper electrode at a position corresponding to the inclined portion of the lower electrode.