| 摘要 |
PURPOSE:To facilitate the insulation of an element by laminating a protective thin film and an ion-sensitive film on a gate electrode which is provided on a conductively active area surface sandwitched by a conductive source region and a drain region arranged on a semi-insulating Ga-As substrate surface layer. CONSTITUTION:An n<+> regions 2 and 2 and an n type active region 3 between the regions 2 and 2 are formed on a semi-insulating GaAs substrate 1 by selective implantation of silicon. Then, a p type buried layer implanted with Be is formed in a region immediate below the region 3 and a Schottkey gate electrode 5 comprising Ti/Pt/Au alloy is formed. Then, an SiO2 protective film 6 is provided over the surface of a wafer and after a part of the film 6 in the regions 2 and 2 is etched off, ohmic electrodes 7 and 7' are formed as drain and source electrodes respectively there. In addition, an SiO2 protective film and an Si3N4 film 8 are formed sequentially and finally, an ion-sensitive film 9 on the active region 3 to obtain an FET ion sensor. Thus, the use of the substrate 1 secures the insulation of the FET thereby providing a sensor of a long life. |
