Semiconductor device having plural bird's beaks of different sizes and manufacturing method thereof

摘要

First bird's beaks are respectively formed in first thermal oxide films at the bottom surface ends and the upper surface ends of a floating gate. In addition, second bird's beaks are formed in second thermal oxide films at the bottom surface ends of a control gate. The dimension of the first thermal oxide films in a gate length direction is smaller than the dimension of the second thermal oxide films in the gate length direction. The first bird's beaks are smaller than the second bird's beaks. In addition, the first bird's beaks are smaller than third bird's beaks (FIG. 12 ) which are formed in third thermal oxide films at the bottom surface ends of the gate electrode (polysilicon film) of a transistor for a peripheral circuit.