A manufacturing method of a semiconductor device is provided for improving the reliability of a semiconductor device including a MISFET with a high dielectric constant gate insulator and a metal gate electrode. A first Hf-containing insulating film containing Hf, La, and O as a principal component is formed as a high dielectric constant gate insulator for an n-channel MISFET. A second Hf-containing insulating film containing Hf, Al, and O as a principal component is formed as a high dielectric constant gate insulator for a p-channel MISFET. Then, a metal film and a silicon film are formed and patterned by dry etching to thereby form first and second gate electrodes. Thereafter, parts of the first and second Hf-containing insulating films not covered with the first and second gate electrodes are removed by wet etching. At this time, a wet process with an acid solution not containing hydrofluoric acid, and another wet process with an alkaline solution are performed, and then a further wet process with an acid solution containing hydrofluoric acid is performed.