Methods for forming a semiconductor device using tilted reactive ion beam

A semiconductor device comprising:

• a gate trench of a vertical transistor structure, wherein the gate trench extends from a front side surface of a semiconductor substrate into the semiconductor substrate;
• and
• a gate electrode located within the gate trench, wherein the gate electrode comprises a slanted or triangular top;
• wherein at least one lateral part of an edge surface of the gate trench comprises at least one of a minimal angle between adjacent surface portions of the at least one lateral part of the edge surface larger than 100° and a minimal radius of curvature of the at least one lateral part of the edge surface larger than 100 nm;
• and
• wherein the at least one lateral part of the edge surface extends from the front side surface of the semiconductor substrate to a side wall of the trench.

A semiconductor device comprising:

• a gate trench of a vertical transistor structure, wherein the gate trench extends from a front side surface of a semiconductor substrate into the semiconductor substrate;
• and
• an insulating layer with vertically varying thickness covering a side wall of the gate trench,
• wherein the insulating layer comprises a lower portion, an upper portion having a thickness less than a thickness of the lower portion, and a beveled portion between the lower portion and the upper portion, and
• wherein the upper portion of the insulating layer has a bevel at the front side surface of the semiconductor substrate.