Semiconductor device

A semiconductor device, comprising:

• a semiconductor substrate;
• an isolation structure in the semiconductor substrate;
• a gate electrode over the semiconductor substrate;
• a channel region between the semiconductor substrate and the gate electrode;
• a pair of source/drain regions adjacent to two opposing sides of the channel region in a channel length direction;
• and
• a threshold voltage adjusting region covering a sidewall and a bottom of the isolation structure.

A semiconductor device, comprising:

• a semiconductor substrate;
• a gate electrode over the semiconductor substrate;
• a channel region between the semiconductor substrate and the gate electrode;
• a pair of source/drain regions adjacent to two opposing sides of the channel region in a channel length direction;
• a pair of isolation structures adjacent to two opposing sides of the channel region in a channel width direction, and extending along the channel length direction;
• and
• a pair of threshold voltage adjusting regions between the channel region and the pair of isolation structures respectively, wherein the pair of threshold voltage adjusting regions and the channel region have the same doping type, and the pair of threshold voltage adjusting regions extend along the channel length direction, wherein the pair of threshold voltage adjusting regions are structurally disconnected from each other.