This paper describes the characteristics of a piezoresistive pressure sensor fabricated on a SOI (Si-on-insulator) structure, in which the SOI structures of Si/SiO₂/Si and Si/Al₂O₃/Si were formed by SDB (Si-wafer direct bonding) technology and hetero-epitaxial growth, respectively. The SOI pressure sensors using the insulator of a SOI structure as the dielectrical isolation layer of piezoresistors, were operated at higher temperatures up to 300 . In the case of pressure sensors using the insulator of a SOI structure as an etch-stop layer during the formation of thin Si diaphragms, the pressure sensitivity variation of the 50I pressure sensors was controlled to within a standard deviation of ±2.3 % over 200 devices. Moreover, the pressure sensors fabricated on the double SOI (Si/Al₂O₃/Si/SiO₂/Si) structures formed by combining SDB technology with epitaxial growth also showed very excellent characteristics with high-temperature operation and high-resolution.