Ion implantation to control formation of mosfet trench-bottom oxide

A method of forming a MOSFET, comprising:

• providing a device structure including a plurality of trenches, the device structure comprising:
• an epitaxial layer over a substrate;
• a well within the epitaxial layer;
• and
• a source region over the well;
• forming an oxide layer within each of the plurality of trenches and over a top surface of the device structure, wherein the oxide layer is formed after the source region is formed over the well;
• implanting just a first portion of the oxide layer using an ion implant delivered to the device structure at a non-zero angle of inclination relative to a perpendicular extending from the top surface of the device structure;
• and
• removing the oxide layer from the top surface of the device structure and from a sidewall of each of the plurality of trenches, wherein a second portion of the oxide layer remains along a bottom of each of the plurality of trenches.

A method of forming a semiconductor device, comprising:

• providing a device structure including a plurality of trenches, the device structure comprising:
• an epitaxial layer over a substrate;
• a well within the epitaxial layer;
• and
• a source region over the well;
• forming an oxide layer within each of the plurality of trenches and over a top surface of the device structure, wherein a thickness of the oxide layer along the top surface of the device structure is greater than a thickness of the oxide layer along a sidewall of each of the plurality of trenches, and wherein the oxide layer is formed after the source region is formed over the well;
• implanting just a first portion of the oxide layer using an ion implant delivered to the device structure at a non-zero angle of inclination relative to a perpendicular extending from the top surface of the device structure;
• and
• removing the oxide layer from the top surface of the device structure and from a sidewall of each of the plurality of trenches, wherein a second portion of the oxide layer remains along a bottom of each of the plurality of trenches.