| 摘要 |
PURPOSE:To reduce the dependency for applied voltage as well as to obtain the accurate capacity value for the subject semiconductor device by a method wherein, after an SiO2 film having an accurate thickness has been formed on a low density P type Si substrate, a boron-doped polycrystalline Si is coated and the impurity concentration on the substrate surface is increased through the intermediary of the SiO2 film. CONSTITUTION:A field oxide film 2 of 8,000Angstrom thickness, an N-channel MOSFET section oxide film 3 of 800Angstrom thicness and an MOS structure capacity section oxide film 4 are formed on the P type Si substrate 1 having the impurity density of 10<15>cm<-3>.Then, source and drain regions 7 and 7' of an FET section are formed by coating and patterning a polycrystalline Si layer 5 and a nitriding Si film 6. Subsequently, the surfaces of the regions 7 and 7' is covered by an oxide film 8 and after the nitriding film 6 has been removed, boron is doped on the polycrystalline Si layer 5. Then, a heat treatment is performed and the concentration of the Si surface is increased to 10<18>cm<-3>by doping boron on the Si surfaces 12 and 13 on the gate section of the MOS structure capacity section FET through the intermediary of the oxide films 3 and 4. Through these procedures, an MOS type element, having least applied voltage dependency and accurate capacity value, can be obtained. |
