A semiconductor device manufacturing method includes: removing an insulating film on a semiconductor substrate by etching and subsequently oxidizing a surface of the semiconductor substrate by using a liquid oxidation agent without exposing this surface to an atmosphere, thereby forming a first insulating film containing an oxide of a constituent element of the semiconductor substrate on the surface of the semiconductor substrate; forming a second insulating film containing an aluminum oxide on the first insulating film; forming a third insulating film containing a rare earth oxide on the second insulating film; forming a high-k insulating film on the third insulating film; introducing nitrogen into the high-k insulating film to thereby make it a fourth insulating film; and conducting heat treatment to change the first through third insulating films into a insulating film made of a mixture containing aluminum, a rare earth element, the constituent element of the semiconductor substrate, and oxygen.