Semiconductor devices and methods of manufacturing thereof

A semiconductor device, comprising:

• a semiconductor substrate;
• a first semiconductor structure of a first conductivity type formed over the semiconductor substrate;
• a second semiconductor structure of a second conductivity type formed over the semiconductor substrate;
• a third semiconductor structure of the first conductivity type formed over the semiconductor substrate, wherein the second semiconductor structure is disposed between the first and second semiconductor structures along a direction;
• a first high-voltage transistor having:
• a first source/drain structure formed in the first semiconductor structure;
• a first gate structure formed over the first and second semiconductor structures;
• a second gate structure formed over the second semiconductor structure;
• and
• a second source/drain structure formed in the second semiconductor structure;
• and
• a second high-voltage transistor having:
• the second source/drain structure;
• a third gate structure formed over the third and second semiconductor structures;
• a fourth gate structure formed over the second semiconductor structure;
• and
• a third source/drain structure formed in the third semiconductor structure.

A method for making a semiconductor device, comprising:

• forming a three-dimensional semiconductor structure protruding from a surface of a semiconductor substrate;
• defining a first region, a second region, and a third region in the three-dimensional semiconductor structure, wherein the first and third regions have a first conductivity type and the second region has a second conductivity type;
• forming a first source/drain structure in the first region, a second source/drain structure in the second region, and a third source/drain structure in the third region;
• and
• forming a first gate structure, a second gate structure, a third gate structure, and a fourth gate structure;
• wherein the first gate structure straddles a portion of the first region and a first portion of the second region, the second gate structure straddles a second portion of the second region, the third gate structure straddles a portion of the third region and a third portion of the second region, and the fourth gate structure straddles a fourth portion of the second region.