Semiconductor device

A semiconductor device, comprising:

• a semiconductor substrate;
• a first semiconductor device, comprising:
• a first gate dielectric in the semiconductor substrate having an upper surface flush with an upper surface of the semiconductor substrate;
• a first gate electrode disposed over the first gate dielectric, wherein the first gate electrode partially covers and partially exposes the upper surface of the first gate dielectric;
• and
• a pair of first source/drain regions on opposing sides of the first gate dielectric;
• and
• a second semiconductor device, comprising:
• a second gate dielectric over the semiconductor substrate having an upper surface higher than the upper surface of the semiconductor substrate;
• a second gate electrode disposed over the second gate dielectric;
• and
• a pair of second source/drain regions on opposing sides of the second gate dielectric.

A semiconductor device, comprising:

• a semiconductor substrate;
• a gate dielectric in the semiconductor substrate having a concave profile that defines an upper boundary lower than an upper surface of the semiconductor substrate;
• a gate electrode disposed over the gate dielectric;
• a pair of source/drain regions on opposing sides of the gate dielectric;
• and
• an inter-layer dielectric covering the gate electrode, wherein a thickness of the inter-layer dielectric is smaller than a sum of a thickness of the gate dielectric and a thickness of the gate electrode.