Lateral MOSFET

A method comprising:

• forming a plurality of isolation regions in a substrate, wherein a first isolation region is in a high voltage region of the substrate, a second isolation region and a third isolation region are in a low voltage region of the substrate, and a fourth isolation region is in both the high voltage region and the low voltage region of the substrate;
• removing an upper portion of the first isolation region to form a trench;
• depositing a high voltage gate dielectric layer over the substrate;
• removing the high voltage gate dielectric layer over the low voltage region;
• depositing a low voltage gate dielectric layer over the low voltage region;
• depositing a gate electrode layer over the high voltage gate dielectric layer and the low voltage gate dielectric layer;
• and
• patterning the gate electric layer to form a first gate electrode region over the first isolation region, a second gate electrode region between the second isolation region and the third isolation region, and a third gate electrode region over the fourth isolation region, where a bottom surface of the first gate electrode region is higher than a bottom surface of the second gate electrode region.

A method comprising:

• forming a first isolation region in a high voltage region of a substrate and a second isolation region at a boundary between the high voltage region and a low voltage region, wherein a top surface of the first isolation region is level with a top surface of the second isolation region;
• removing an upper portion of the first isolation region to form a recess;
• depositing a gate dielectric layer over the first isolation region and the second isolation region;
• forming a gate electrode layer over the gate dielectric layer;
• and
• patterning the gate electrode layer to form a first gate electrode region over the first isolation region and a second gate electrode region over the second isolation region wherein:
• the first gate electrode region comprise a first portion over the first isolation region and a second portion over the substrate, and where a top surface of the first portion is lower than a top surface of the second portion.