Invention Grant
- Patent Title: Three-dimensional memory device containing multi-threshold-voltage drain select gates and method of making the same
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Application No.: US15850073Application Date: 2017-12-21
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Publication No.: US10347647B1Publication Date: 2019-07-09
- Inventor: Naohiro Hosoda , Keisuke Shigemura , Junichi Ariyoshi , Kazuki Kajitani , Yuji Fukano
- Applicant: SANDISK TECHNOLOGIES LLC
- Applicant Address: US TX Addison
- Assignee: SANDISK TECHNOLOGIES LLC
- Current Assignee: SANDISK TECHNOLOGIES LLC
- Current Assignee Address: US TX Addison
- Agency: The Marbury Law Group PLLC
- Main IPC: H01L27/115
- IPC: H01L27/115 ; H01L27/11556 ; H01L27/11519 ; H01L27/11565 ; H01L27/11582 ; H01L27/1157 ; H01L21/265 ; H01L21/266 ; H01L27/11524 ; H01L29/40

Abstract:
A memory device contains a stack of insulating layers and electrically conductive word line layers, at least one first drain select gate electrode located over the stack and extending through a first drain select transistor and a second drain select transistor, at least one second drain select gate electrode located between the first drain select electrode and the stack, and extending through a third drain select transistor and a fourth drain select transistor. The first drain select transistor and the third drain select transistor are located in a first NAND memory string. The second drain select transistor and the fourth drain select transistor are located in a second NAND memory string different from the first NAND memory string. The first drain select transistor has a higher threshold voltage than the second drain select transistor. The third drain select transistor has a lower threshold voltage than the fourth drain select transistor.
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