Nonvolatile semiconductor memory device and manufacturing process thereof

• US 6,255,691 B1
• Filed: 12/18/1998
• Issued: 07/03/2001
• Est. Priority Date: 12/19/1997
• Status: Expired due to Term

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Hashimoto, Koji
• Primary Examiner(s): WOJCIECHOWICZ, EDWARD JOSEPH
• Application Number:
  US09/216,292
• Time in Patent Office: 928 Days
• Field of Search: 257/321, 257/315, 438/211, 438/230, 438/257, 438/267
• US Class Current: 257/321
• CPC Class Codes: H01L 29/40114 the electrodes comprising a conductor-insulator-conductor-insulator-semiconductor structure
• CPC Class Codes: H01L 29/42324 Gate electrodes for transistors with a floating gate
• CPC Class Codes: H01L 29/66825 with a floating gate H01L29/6684 takes precedence
• CPC Class Codes: H10B 41/30 characterised by the memory core region
• CPC Class Codes: H10B 41/35 with a cell select transistor, e.g. NAND
• CPC Class Codes: H10B 69/00 Erasable-and-programmable ROM [EPROM] devices not provided for in groups H10B41/00 - H10B63/00, e.g. ultraviolet erasable-and-programmable ROM [UVEPROM] devices

Abstract

A floating gate electrode 11 has: a conductive side wall 23 located above a tunnel window 13a, a main part electrode 9 located in the vicinity of the tunnel window 13a and above a channel region 10, and a connecting part 25. The connecting part 25 is located between the conductive side wall 23 and the main part electrode 9 to interconnect the conductive side wall 23 and the main part electrode 9. The region that substantially functions as the tunnel window is determined with the width W1 of the conductive side wall 23.

Claims

1. A nonvolatile semiconductor memory device comprising:

a semiconductor substrate;

first regions provided in the semiconductor substrate;

a second region provided so as to form a region capable of creating an electric channel between the first regions;

a first insulation film provided to extend over one of the first regions and the region capable of creating an electric channel, the first insulation film having a thin film portion of a thickness smaller on at least a portion of said one of the first regions than on the region capable of creating an electric channel;

a floating electrode provided over the first insulation film to store electric charges;

the floating electrode having a conductive side wall located over the thin film portion, and a main part located in the vicinity of the thin film portion and above the region capable of creating an electric channel, said floating electrode also having an isolation layer and a conductive connection part such that a lower region formed between the side wall and the main part is electrically isolated by the isolation layer and an upper region formed between the side wall and the main part is electrically connected by the conductive connection part;

a second insulation film provided on the floating electrode; and

a control electrode provided on the second insulation film.

2. A nonvolatile semiconductor memory device comprising:

a semiconductor substrate of a first conductive type to form a first conductive type region;

a second conductive type region formed in the semiconductor substrate;

a tunnel oxide film formed on at least a portion of the first conductive type region comprising a thin film portion over at least a portion of the second conductive type region; and

a floating electrode, capable of switching between write and non-write states by transferring electric charges to and from the second conductive type region through the thin film portion, comprising;

a conductive side wall located over the thin film portion;

a main part located in the vicinity of the thin film portion and above at least part of the tunnel oxide film; and

an isolation layer and a conductive connection part such that a lower region formed between the conductive side wall and the main part is electrically isolated by the isolation layer and an upper region formed between the conductive side wall and the main part is electrically connected by the conductive connection part.

3. A process for manufacturing the nonvolatile semiconductor memory device capable of switching between write and non-write states by transferring electric charges between a floating electrode and in a substrate a conductive type region through a thin film portion of a tunnel oxide film, comprising the steps of:

forming an insulation film on the substrate and forming a main part of the floating electrode for storing electric charges on the insulation film;

partially removing the insulation film around a side wall of the floating electrode using the floating electrode as a mask;

forming an oxide film of a predetermined thickness thinner than the insulation film on at least the main part and on the substrate where the insulation film has been removed, thereby from the insulation film and the oxide film forming the tunnel oxide film having the thin film portion;

forming the conductive side wall on the insulation film on the side wall of the main part and on the thin film portion; and

partially removing the insulation film formed between the main part and the conductive side wall, thereby avoiding completely insulating so that there can be an electrical connection between the conductive side wall and an upper region of the main part.

4. The process for manufacturing the nonvolatile semiconductor memory device of claim 3, wherein the conductive side wall is formed on the side wall of the main part and the thin film portion by an isotropic etching after forming a conductive material layer over the entire surface.

5. The process for manufacturing the nonvolatile semiconductor memory device of claim 3, wherein a conductive type of impurities is implanted into the substrate while using the floating electrode as a mask when the insulation film around the side wall of the floating electrode is partially removed.

6. The process for manufacturing the nonvolatile semiconductor memory device of claim 3, wherein the electric interconnection between a side surface of the main part and a side wall is made by depositing a conductive layer after the insulation film between the main part side wall and the conductive side wall is partially removed.