Optical device including gate insulating layer having edge effect

An optical device comprising:

• a semiconductor substrate;
• an insulator formed over the semiconductor substrate;
• a first semiconductor layer which is formed over the insulator and has a recessed groove having first and second sidewalls that are substantially vertical;
• a gate insulating layer formed over the groove and over the first semiconductor layer along the contour of the recessed groove;
• a second semiconductor layer formed over the gate insulating layer;
• and
• at least one ohmic layer, which is doped with high density impurities, configured to form an ohmic contact with the second semiconductor layer,
• wherein the recessed groove has a bottom wall, the first and second sidewalls being substantially orthogonal to the bottom wall.

An optical device comprising:

• a semiconductor substrate;
• an insulator formed over the semiconductor substrate;
• a first semiconductor layer which is formed over the insulator and has a recessed groove having first and second sidewalls that are substantially vertical;
• a gate insulating layer formed over the groove and over the first semiconductor layer along the contour of the recessed groove;
• a second semiconductor layer formed over the gate insulating layer;
• and
• wherein the gate insulating layer comprises a first insulating layer and a second insulating layer, the second insulating layer formed over a bottom wall and the first and second sidewalls of the groove and extending over the first semiconductor layer, the first insulating layer interposed between the second insulating layer and the first semiconductor layer.