GaN-based high electron mobility transistor (HEMT) with an embedded gate electrode having a first recess portion and a second recess portion to improve drain breakdown voltage

A semiconductor device comprising:

• a substrate;
• a GaN-based semiconductor layer formed on the substrate;
• a gate electrode embedded in the GaN-based semiconductor layer;
• a source electrode and a drain electrode formed on opposing sides of the gate electrode;
• a first recess portion formed between an embedded portion of the gate electrode and the source electrode;
• and
• a second recess portion formed between the embedded portion of the gate electrode and the drain electrode,
• wherein the GaN-based semiconductor layer in the first recess portion has a thickness larger than that of the GaN-based semiconductor layer in the second recess portion;
• wherein a first part of the gate electrode of the drain electrode side is formed directly on the second recess portion and is deeper than a second part of the gate electrode formed directly on the first recess portion;
• and
• wherein the first recess portion has a first bottom plane, the second recess portion has a second bottom plane and the first bottom plane is higher than all parts of the second bottom plane, and
• wherein the embedded portion of the gate electrode has a bottom plane which is lower than the first bottom plane of the first recess portion and the second bottom plane of the second recess portion.