Electronic – Unknown component in an electronic dictionary

I'm exploring the inside of my favorite device, a Japanese electronic dictionary. It runs on AAA batteries and has two screens (one for writing and one for viewing), speakers/headphone jack, a USB connector and an SD card slot.

There's a peculiar component I can't identify. It looks like two plates of metal glued together with a lead from each plate. The simplicity of it makes me think it's a capacitor; however, I've never encountered a capacitor that looks like this, and the huge footprint seems like a waste for a simple capacitor.

Here's a picture of the side of the PCB with the unidentified component. The leads on the top left lead to a keyboard PCB and on the ones on the right lead to the screen. The unidentified component is below the two blobs.

Here's a closeup of the component:

In case it helps (or is interesting!), here's the other side of the PCB: