3D button implementation with plane / cube and leap motion

I am making a UI system that let users can push a button (mesh with box collider) with hand via leap motion.
I used plane with box collider and rigid body, but it doesn't work well.
I need the plane moves in its local z-axis only, and after the finger released, I need the plane pops back to its original position (now it's just pushed away, and along world-z axis).

How can I do to deal with that? Or should I use OnCollisionEnter approach?

Thanks in advance!