Patent ID: 7982257

Claim:
A semiconductor device having a bit line and a word line, the device comprising: a substrate which is provided with first trenches extending in a bit-line direction and has side surfaces forming sidewalls of the first trenches; a first gate insulator formed on the substrate between the first trenches; a floating gate formed on the first gate insulator between the first trenches and located between second trenches extending in a word-line direction, the floating gate having first side surfaces facing the first trenches and second side surfaces facing the second trenches; a second gate insulator formed on the floating gate between the second trenches; and a control gate formed on the second gate insulator between the second trenches, wherein the substrate includes bird's beaks which are provided at upper edges of the side surfaces of the substrate so that the bird's beaks are prevented from being provided at lower edges of the first side surfaces of the floating gate.