iPhone 5 Tilt sensor broken

A week ago, my iPhone5's tilt function disabled, i aware of lock portrait mode, and i'm sure i unlocked it, and I assumed other apps may bothering this tilt function, so i erased everything and restored back to factory setting, and tested with gyroscope, compass, doodle jump and etc however it wasn't moving at all. But when i put assistive control out and forced to rotate, it did rotate.

So i figured out it's something that had to do with hardware

Question is : when tilt function does not work, which part do i have to change? Please guide me to the solution

Thank you