Semiconductor device having a CMOS element as a buffer

A semiconductor device comprising:

• a semiconductor substrate of a first conductivity type;
• a first region of a second conductivity type formed in said semiconductor substrate;
• a first MOS transistor of the second conductivity type formed in said semiconductor substrate except for said first region and having a first electrode coupled to a first voltage level, a second electrode, and a gate electrode;
• a second MOS transistor of the first conductivity type formed in said first region and having a first electrode coupled to the second electrode of said first MOS transistor, a second electrode coupled to a second voltage level higher than the first voltage level, and a gate electrode;
• and
• a second region of the second conductivity type applied to a third voltage level higher than the second voltage level, formed in said first region and substantially surrounding said second MOS transistor in a plan view of the device.

A semiconductor device comprising:

• a semiconductor substrate of a first conductivity type;
• a first region of a second conductivity type formed in said semiconductor substrate;
• a first MOS transistor of the second conductivity type formed in said semiconductor substrate except for said first region and having a first electrode coupled to a first voltage level, a second electrode, and a gate electrode;
• a second MOS transistor of the first conductivity type formed in said first region and having a first electrode coupled to the second electrode of said first MOS transistor, a second electrode coupled to a second voltage level higher than the first voltage level, and a gate electrode;
• a third MOS transistor of the first conductivity type formed in said first region and having a first electrode coupled to the second electrode of said first MOS transistor, a second electrode coupled to the second voltage level, and a gate electrode coupled to the second voltage level;
• and
• a second region of a second conductivity type formed in said first region and applied to a third voltage level higher than the second voltage level.