Mobile terminal including input device having piezoelectric sensor and method of operating the same

A mobile terminal comprising:

• a body;
• and
• a piezoelectric sensor unit comprising a first piezoelectric sensor positioned at a first side surface of the body and to which at least one first function key is set, the at least one first function key, responsive to a first applied pressure, for causing the first piezoelectric sensor to piezoelectrically generate a first signal for performing a first specific function corresponding to a user function of the mobile terminal, and a second piezoelectric sensor positioned at a second side surface of the body and to which at least one second function key is set, the at least one second function key, responsive to a second applied pressure, for causing the second piezoelectric sensor to piezoelectrically generate a second signal for performing a second specific function different than the first specific function.