Semiconductor device and method for fabricating the same

A method for fabricating a semiconductor device, comprising:

• forming a first well region and a second well region both with a first electrical property in a substrate, wherein the first well region and the second well region are separated from each other;
• forming a first gate dielectric layer with a first thickness on the first well region;
• forming a second gate dielectric layer with a second thickness on the second well region, wherein the first gate dielectric layer and the second gate dielectric layers are separated from each other, and the first thickness is greater than the second thickness;
• forming a first gate electrode on the first gate dielectric layer;
• forming a second gate electrode on second gate dielectric layer, wherein the second gate electrode and the first gate electrode are separated from each other;
• forming a drain region in the first well region;
• and
• forming a source region in the second well region.