Semiconductor device and method for fabricating the same

A method for fabricating a semiconductor device, comprising:

• providing a semiconductor substrate;
• forming a semiconductor layer over the semiconductor substrate;
• forming a first well region in the semiconductor layer and the semiconductor substrate;
• forming a second well region in the semiconductor layer, being adjacent to the first well region;
• forming a first isolation element in the first well region and a second isolation element in the second well region;
• forming a gate structure in the first and second well regions, and between the first and second isolation elements;
• and
• forming a first doped region in the first well region and a second doped region in the second well region, wherein the semiconductor substrate, the semiconductor layer, and the second well region have a first conductivity type, and the first well region, the first doped region, and the second doped region have a conductivity type that is opposite to the first conductivity type, and a bottom surface of the gate structure is above, lower than or level with a bottom surface of the first isolating element.