In one example, a method of forming a bulk acoustic wave (BAW) resonator comprises: forming an electrode on at least one of a semiconductor substrate, a sacrificial layer, or an acoustic reflector; and forming a piezoelectric layer on the electrode, the piezoelectric layer having a convex surface.

An elastic wave device includes a supporting substrate, an acoustic multilayer film on the supporting substrate, a piezoelectric substrate on the acoustic multilayer film, and an IDT electrode on the piezoelectric substrate. An absolute value of a thermal expansion coefficient of the piezoelectric substrate is larger than an absolute value of a thermal expansion coefficient of the supporting substrate. The acoustic multilayer film includes at least four acoustic impedance layers. The elastic wave device further includes a bonding layer provided at any position in a range of from inside the first acoustic impedance layer from the piezoelectric substrate side towards the supporting substrate side, to an interface between the third acoustic impedance layer and the fourth acoustic impedance layer.

An elastic wave device includes a supporting substrate, an acoustic multilayer film on the supporting substrate, a piezoelectric substrate on the acoustic multilayer film, and an IDT electrode on the piezoelectric substrate. The acoustic multilayer film includes at least four acoustic impedance layers. The at least four acoustic impedance layers include at least one low acoustic impedance layer and at least one high acoustic impedance layer having an acoustic impedance higher than the low acoustic impedance layer. The elastic wave device further includes a bonding layer provided at any position in a range of from inside the acoustic impedance layer, which is the fourth acoustic impedance layer from the piezoelectric substrate side towards the supporting substrate side, to an interface between the acoustic multilayer film and the supporting substrate.

The present disclosure provides a piezoelectric resonator, including a bottom electrode, a piezoelectric layer formed on a side of the bottom electrode, a top electrode formed on a side of the piezoelectric layer away from the bottom electrode, an acoustic wave reflection structure formed on a side of bottom electrode away from piezoelectric layer, an insertion layer, and a mass load. The top electrode, piezoelectric layer, bottom electrode, and acoustic wave reflection structure form a resonant region. The insertion layer is formed on a side of top electrode away from piezoelectric layer and/or on the side of bottom electrode away from piezoelectric layer, and at least partially covers the resonant region. The mass load is formed on a side of the insertion layer away from piezoelectric layer, and is at least partially formed in the resonant region. The piezoelectric resonator has high performance, lower process difficulty, higher manufacturability and yield.

Method of forming a termination angle in a titanium tungsten layer include providing a titanium tungsten layer and applying a photo resist material to the titanium tungsten layer. The photo resist material is exposed under a defocus condition to generate a resist mask, wherein an edge of the exposed photo resist material corresponds to the sloped termination. The titanium tungsten layer is etched with an etching material, wherein the etching material at least partially etches the photo resist material exposed under the defocused condition, and wherein the etching results in the sloped termination in the titanium tungsten layer.

A piezoelectric device includes a foundation structure and a plurality of metal islands distributed over a first area of a top surface of the foundation structure. A piezoelectric film resides over the foundation structure and is formed from a piezoelectric material. The piezoelectric film has a non-piezoelectric portion over the first area and a piezoelectric portion over a second area of the top surface of the foundation structure. Within the non-piezoelectric portion, the piezoelectric film is polarity patterned to have pillars and a mesh. The pillars of the piezoelectric material have a first polar orientation residing over corresponding ones of the plurality of metal islands. The mesh of the piezoelectric material has a second polar orientation, which is opposite that of the first polar orientation, and surrounds the pillars. In one embodiment, the metal islands are self-assembled islands.

An elastic wave device includes an interdigital transducer electrode including electrode fingers provided on a first principal surface of a piezoelectric thin film. A conductive layer is provided on a second principal surface of the piezoelectric thin film. An elastic wave propagates in the piezoelectric thin film in an S0 mode of a plate wave, and a piezoelectric thin film portion in a region below spaces between the electrode fingers of the interdigital transducer electrode is displaced by a greater amount than each electrode finger and a piezoelectric thin film portion in a region below each electrode finger.

Embodiments provide a solidly-mounted bulk acoustic wave (BAW) resonator and method of making same. In embodiments, the BAW resonator may include a planzarization portion in an inactive region of the BAW resonator that is coplanar with a piezoelectric layer of the BAW resonator in an active region of the BAW restonator. Other embodiments may be described and claimed.

Disclosed is an acoustic wave resonator comprising a substrate material formed of aluminum nitride (AIN) doped with one or more of zinc (Zn), lithium (Li), silicon (Si), or germanium (Ge) to enhance performance of the acoustic wave resonator.

Resonator structures are provided, as well as methods and structures for generating smooth electrodes and electrode structures with a uniformly smooth surface.