| 摘要 |
PURPOSE:To greatly reduce the variation of threshold voltages after gamma ray irradiation, by restricting the impurity in a gate oxide film from the gate region side within a fixed thickness in a MOS structure. CONSTITUTION:A MOSFET of SOS structure is constituted of a source region 1, a drain region 2, a gate oxide film 3, a gate region 4 and a sapphire substrate 5. In such a constitution, a heat treatment after the formation of the region 4 is so performed at a low temperature for a short time that the depth of impurity infiltration into the film 3 may be 20% or less of the thickness of the film 3 from the region 4 side. Thereby, the shift of the threshold values of a MOSFET due to gamma ray irradiation can be suppressed to a very small degree. |
