Power semiconductor devices including a trenched gate and methods of forming such devices

A semiconductor device comprising:

• a semiconductor layer structure comprising a trench in an upper surface thereof, wherein the trench comprises a rounded upper corner and a rounded lower corner;
• a dielectric layer in a lower portion of the trench, wherein a center portion of a top surface of the dielectric layer is curved, and the dielectric layer is on opposed sidewalls of the trench;
• and
• a gate electrode in the trench and on the dielectric layer opposite the semiconductor layer structure),
• wherein each of the rounded upper corner and the rounded lower corner has a radius of curvature in a range of 0.01 microns to 0.5 microns.

A semiconductor device comprising:

• a semiconductor layer structure comprising a trench in an upper surface thereof, wherein the trench comprises a rounded upper corner and a rounded lower corner;
• a bottom dielectric layer in a lower portion of the trench;
• a gate dielectric layer on a sidewall of the trench and on the bottom dielectric layer;
• and
• a gate electrode in the trench and on the gate dielectric layer opposite the semiconductor layer structure,
• wherein the bottom dielectric layer comprises a first concentration of an additive, and the gate dielectric layer has a second concentration of the additive that is lower than the first concentration.

A semiconductor device comprising:

• a semiconductor layer structure comprising a trench in an upper surface thereof, wherein the trench comprises a rounded upper corner and a rounded lower corner;
• a bottom dielectric layer in a lower portion of the trench;
• a gate dielectric layer on a sidewall of the trench and on the bottom dielectric layer, the gate dielectric layer comprising a material different from the bottom dielectric layer;
• and
• a gate electrode in the trench and on the gate dielectric layer opposite the semiconductor layer structure,
• wherein the bottom dielectric layer comprises an additive, and the additive comprises boron (B), phosphorous (P), sodium (Na), potassium (K), lithium (Li), calcium (Ca), magnesium (Mg), and/or lead (Pb).

A semiconductor device comprising:

• a semiconductor layer structure comprising a trench in an upper surface thereof, wherein the trench comprises a rounded lower corner;
• a dielectric layer in a lower portion of the trench, wherein a center portion of a top surface of the dielectric layer is curved;
• and
• a gate electrode in the trench and on the dielectric layer opposite the semiconductor layer structure,
• wherein the semiconductor layer structure comprises a drift layer having a first conductivity type, a well having a second conductivity type in an upper portion of the drift layer and a source region having the first conductivity type in an upper portion of the well, and
• wherein the dielectric layer comprises:
• a bottom dielectric layer on a bottom surface of the trench and on lower portions of sidewalls of the trench, the bottom dielectric layer comprising a rounded lower corner;
• and
• a gate dielectric layer on upper portions of the sidewalls of the trench and on the bottom dielectric layer.