| 摘要 |
In a trenched MOS gate power device having a trenched MOS gate structure, a gate insulating film is formed on the walls of trenches to extend onto a major surface of a semiconductor substrate, and gates are formed so as to fill up the trenches and to extend onto the gate insulating film on the major surface of the semiconductor substrate. The gate insulating film is formed so that the thickness of a portion thereof formed on the major surface of the semiconductor substrate is greater than that of a portion thereof formed on the walls of the trenches to narrow portions of the gates corresponding to the tops of the trenches. Thus, the characteristics of a gate insulating film formed on the walls of trenches are improved.
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