Ion implantation to form trench-bottom oxide of MOSFET

A method of forming a MOSFET, comprising:

• providing a device structure including a well formed in an epitaxial layer;
• forming a plurality of trenches through the well and the epitaxial layer;
• forming a mask over the device structure including within each of the plurality of trenches and over a top surface of the device structure, wherein a thickness of the mask along the top surface of the device structure is greater than a thickness of the mask within each of the plurality of trenches;
• removing the mask from within each of the plurality of trenches, wherein the mask remains along the top surface of the device structure;
• and
• implanting the device structure to form a treated layer along a bottom of each of the plurality of trenches.

A method of forming a MOSFET trench-bottom oxide, comprising:

• providing a device structure including a well formed in an epitaxial layer;
• forming a plurality of trenches through the well and the epitaxial layer;
• forming a hardmask over the device structure including within each of the plurality of trenches and over a top surface of the device structure, wherein a thickness of the hardmask along the top surface of the device structure is greater than a thickness of the hardmask within each of the plurality of trenches;
• removing the hardmask from within each of the plurality of trenches, wherein the hardmask remains along the top surface of the device structure;
• implanting the device structure to form a treated layer along a bottom of each of the plurality of trenches;
• and
• forming a gate oxide layer along a sidewall of each of the plurality of trenches and along the bottom of each of the plurality of trenches, wherein a thickness of the gate oxide layer along the bottom of each of the plurality of trenches is greater than a thickness of the gate oxide layer along the sidewall of each of the plurality of trenches.