A voltage-controlled oscillator includes a piezoelectric element, a first package, an electronic element, and a second package. The first package contains the piezoelectric element. The second package contains the electronic element and the first package. The second package includes a base, and a lid. The electronic element and the first package are mounted in the base. The lid hermetically seals the electronic element and the first package together with the base. The base includes a substrate part, a first frame part, and a second frame part. The substrate part includes a first major face and a second major face opposite to the first face. The electronic element is mounted on the first major face. The first frame part includes a first frame face on which the first package is mounted. The first frame part is located on a peripheral edge of the first major face.

A resonator device includes: a resonator element; a first package accommodating the resonator element; a heater bonded to the first package; and a second package accommodating the first package and the heater. The first package includes: a base substrate that has a first surface on which the resonator element is disposed and a second surface in a front-back relation with the first surface, and that contains single crystal silicon; an integrated circuit that is provided on the first surface or the second surface and that includes a temperature sensor; and a lid that is bonded to the base substrate such that the resonator element is accommodated between the lid and the base substrate.

A resonator is provided that includes a vibration part, a frame, and a support arm. The vibration part includes an Si substrate that has a principal surface with a width W in an X-axis direction and a length L in a Y-axis direction. The vibration part is configured to vibrate mainly in a contour vibration mode. The support arm extends in the Y-axis direction and connects the frame to one of two ends in the Y-axis direction of the vibration part. When the principal surface of the Si substrate is viewed in a plan view, the width W is at its maximum Wmax at a point in the Y-axis direction and decreases with increasing proximity to the one of the two end portions in the Y-axis direction of the vibration part and with increasing proximity to the other end portion in the Y-axis direction of the vibration part.

An acoustic wave device includes a support including a support substrate with a thickness in a first direction, a piezoelectric layer on the support in the first direction on the support, and resonators each including a functional electrode on the piezoelectric layer in the first direction on the piezoelectric layer. The support includes space portions therein at positions where the functional electrodes at least partially overlap in a planar view in the first direction. The support includes a lead portion communicating with at least one of the space portions in a planar view in the first direction, at a position that does not overlap the space portion. At least one lead portion communicates with at least two of the space portions. The piezoelectric layer includes a through-hole penetrating the piezoelectric layer at a position overlapping the lead portion in a planar view in the first direction.

An acoustic wave device includes a support including a support substrate with a thickness in a first direction, a piezoelectric layer on the support in the first direction on the support, and resonators each including a functional electrode on the piezoelectric layer in the first direction on the piezoelectric layer. The support includes space portions therein at positions where the functional electrodes at least partially overlap in a planar view in the first direction. The support includes a lead portion communicating with at least one of the space portions in a planar view in the first direction, at a position that does not overlap the space portion. At least one lead portion communicates with at least two of the space portions. The piezoelectric layer includes a through-hole penetrating the piezoelectric layer at a position overlapping the lead portion in a planar view in the first direction.