Semiconductor integrated circuit device with alpha rays resistance

A semiconductor integrated circuit device having alpha rays resistance, said device comprising:

• a semiconductor substrate of a first conductivity type;
• a first semiconductor layer of said first conductivity type having a high concentration of impurity atoms, said layer being formed on a predetermined area of said semiconductor substrate;
• a second semiconductor layer of said first conductivity type having a low concentration of impurity atoms, said layer being formed on said first semiconductor layer;
• a third semiconductor layer of a second conductivity type having a high concentration of impurity atoms, said layer being formed on said second semiconductor layer and being separated from said first semiconductor layer by said second semiconductor layer;
• a fourth semiconductor layer of said second conductivity type having a low concentration of impurity atoms, said layer being formed on said third semiconductor layer;
• and
• at least one isolation region which extends from a surface of said fourth semiconductor layer into said semiconductor substrate with said isolation region penetrating said first semiconductor layer.