A composition for forming a ferroelectric thin film includes: a PZT sol-gel solution including at least one of: a whole or partial hydrolysate of a lead precursor and a whole or partial hydrolyzed and polycondensated product thereof; a whole or partial hydrolysate of a zirconium precursor, a whole or partial hydrolyzed and polycondensated product thereof, and a zirconium complex having at least one hydroxy ion and at least one non-hydrolyzable ligand; and a whole or partial hydrolysate of a titanium precursor, a whole or partial hydrolyzed and polycondensated product thereof, and a titanium complex having at least one hydroxyl ion and at least one non-hydrolyzable ligand; and a Bi2SiO5 sol-gel solution including at least one of: a whole or partial hydrolysate of a silicon precursor and a whole or partial hydrolyzed and polycondensated product thereof, and a resultant obtained by refluxing triphenyl bismuth as a bismuth precursor.