After a TEOS oxide film is formed on the surface of a semiconductor device, a PSG film and an SiN film, which have air permeability, are formed on the surface of the TEOS oxide film. Thereafter, a Poly-Si film is formed thereon. A sacrifice layer is removed by a gaseous HF that passes through the PSG film, the SiN film, and the Poly-Si film, and then, the uppermost layer is covered with a Poly-Si/SiC film. A chip scale package having a thin-film hollow-seal structure can be realized on the semiconductor element.