| CPC H01L 21/28158 (2013.01) [H01L 21/76202 (2013.01); H10D 62/115 (2025.01); H10D 64/511 (2025.01); H10D 84/83 (2025.01)] | 20 Claims |

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1. A semiconductor device, comprising:
a recess along a top surface of a semiconductor substrate, the recess having a first sidewall and a second sidewall laterally opposite each other;
a nitride-based spacer layer extending along the first sidewall of the recess, wherein the second sidewall is defined by a shallow trench isolation (STI) structure extending into the semiconductor substrate; and
a field oxide layer in the recess extending along a bottom surface of the recess, wherein a lateral tip of the field oxide layer is blocked by the nitride-based spacer layer from laterally extending beyond the first sidewall into the semiconductor substrate.
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