Patent ID: 9673289
Date: 2017-06-06
CPC Classifications: H01L

Claim:
1. A power metal-oxide-silicon field effect transistor (MOSFET) device, comprising: a semiconductor layer of a first conductivity type; an active trench formed in the semiconductor layer, the active trench having a first trench depth and housing a dual oxide thickness trench gate structure including a first trench gate formed in the active trench, the first trench gate being isolated from a sidewall of the semiconductor layer by a gate oxide layer in an upper portion of the active trench and being isolated from the sidewall of the semiconductor layer by a first liner oxide layer in a bottom portion of the active trench, the first liner oxide layer being formed between the first trench gate and the sidewall of the semiconductor layer in a lateral direction, the first liner oxide layer being thicker than the gate oxide layer, a bottom of the first trench gate being isolated from a bottom of the active trench by the first liner oxide layer having a first thickness; and a termination trench formed in the semiconductor layer apart from the active trench, the termination trench having a second trench depth deeper than the first trench depth and housing a dual oxide thickness trench gate structure including a second trench gate formed in the termination trench, the second trench gate being isolated from the sidewall of the semiconductor layer on a first side of the termination trench by a first sidewall oxide layer in an upper portion of the termination trench and by a second liner oxide layer in a bottom portion of the termination trench, the second liner oxide layer being formed between the second trench gate and the sidewall of the semiconductor layer on the first side in a lateral direction, the second liner oxide layer being thicker than the first sidewall oxide layer, the second trench gate being isolated from the sidewall of the semiconductor layer on a second, opposite side of the termination trench by a second sidewall oxide layer, a bottom of the second trench gate being isolated from a bottom of the termination trench by the second liner oxide layer having a second thickness greater than the first thickness.