US20220085034A1

US20220085034A1 - Fuse array structure

Info

Publication number: US20220085034A1
Application number: US17/534,848
Authority: US
Inventors: Shian-Jyh Lin
Original assignee: Nanya Technology Corp
Current assignee: Nanya Technology Corp
Priority date: 2018-12-27
Filing date: 2021-11-24
Publication date: 2022-03-17
Also published as: US11456303B2; TW202025453A; US20200212049A1; TWI722668B; CN111384055B; CN111384055A

Abstract

The present disclosure provides a semiconductor structure with a fuse array structure having a buried word line disposed within a substrate. The semiconductor structure includes a substrate having a first surface, a first doped region disposed under the first surface, a second doped region disposed under the first surface, and a recess indented into the substrate and disposed between the first doped region and the second doped region; a first gate structure disposed over the first doped region and electrically connected to a first bit line; a second gate structure to disposed over the first surface of the substrate and electrically connected to a second bit line; and a buried word line disposed within the first recess and disposed between the first gate structure and the second gate structure. The second gate structure is at least partially disposed within the second recess of the substrate.

Description

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the priority benefit of U.S. provisional application Ser. No. 62/785,359 filed on Dec. 27, 2018. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. Non-Provisional Application No. 16/677,104 filed on Oct. 29, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The present disclosure relates to a semiconductor structure, and particularly relates to a fuse array structure having a buried word line disposed within a substrate.

DISCUSSION OF THE BACKGROUND

Semiconductor devices are essential for many modern applications. Among the semiconductor devices, memory devices such as dynamic random access memory (DRAM) have assumed an important role. The memory device includes several memory cells arranged in rows and columns over a substrate, and information of each memory cell is accessible by bit lines and word lines extending over a surface of the substrate.
With the advancement of electronic technology, capacity of a fuse array structure continues to increase. In other words, a density of the fuse array structure arranged over the substrate is increased. Accordingly, it is difficult to maintain sufficient isolation between electrical components in the fuse array structure.
Therefore, there is a continuous need to improve a structural configuration of the semiconductor device.
This Discussion of the Background section is provided for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this Discussion of the Background section constitutes prior art to the present disclosure, and no part of this Discussion of the Background section may be used as an admission that any part of this application, including this Discussion of the Background section, constitutes prior art to the present disclosure.

SUMMARY

One aspect of the present disclosure provides a semiconductor structure comprising a substrate including a first surface, a first doped region disposed under the first surface, a second doped region disposed under the first surface, and a recess indented into the substrate and disposed between the first doped region and the second doped region; a control gate structure disposed over the first doped region and electrically connected to a control bit line; a fuse gate structure disposed over the second doped region and electrically connected to a fuse bit line; and a buried word line disposed between the control gate structure and the fuse gate structure, wherein the buried word line is disposed within the recess of the substrate.
In some embodiments, the buried word line is disposed under and away from the first surface of the substrate.
In some embodiments, the buried word line is disposed under and away from the first doped region and the second doped region.
In some embodiments, the recess extends from the first surface of the substrate towards a second surface of the substrate opposite to the first surface.
In some embodiments, the fuse gate structure includes a fuse dialetric disposed on the second doped region.
In some embodiments, the fuse dielectric is breakable when a voltage bias between the buried word line and the fuse bit line is substantially greater than 5V.
In some embodiments, the buried word line is disposed under and away from the fuse electric.
In some embodiments, the fuse dielectric includes oxide or metal contained oxide.
In some embodiments, the first doped region and the second doped region are of a same conductive type.
In some embodiments, the buried word line includes a conductor and an isolation layer disposed within the recess and between the substrate and the conductor.
In some embodiments, the isolation layer is disposed conformal to a sidewall of the recess.
In some embodiments, the isolation layer includes a first portion disposed between the conductor and the substrate, and a second portion disposed under the conductor, and wherein a thickness of the first portion is substantially greater than a thickness of the second portion.
In some embodiments, the isolation layer includes high-k (high dialetric constant) dialectric material.
In some embodiments, the control bit line and the fuse bit line are substantially orthogonal to the buried word line.
In some embodiments, the control bit line and the fuse bit line are substantially parallel to each other.
Another aspect of the present disclosure provides a semiconductor structure comprising a substrate including a first surface, a first doped region disposed under the first surface, a second doped region disposed under the first surface, a first recess indented into the substrate and disposed between the first doped region and the second doped region, and a second recess indented into the substrate and adjacent to the second doped region; a first gate structure disposed over the first doped region and electrically connected to a first bit line; a second gate structure disposed over the first surface of the substrate and electrically connected to a second bit line; and a buried word line disposed within the first recess and disposed between the first gate structure and the second gate structure, wherein the second gate structure is at least partially disposed within the second recess of the substrate.
In some embodiments, a depth of the second recess is substantially less than a depth of the first recess.
In some embodiments, the second gate structure includes a gate dialectric disposed within the second recess of the substrate.
In some embodiments, the gate dielectric is breakable upon a voltage bias between the buried word line and the second bit line.
In some embodiments, the voltage bias between the buried word line and the second bit line is substantially greater than 2V.
The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter, and form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure may be derived by referring to the detailed description and claims when considered in connection with the Figures, where like reference numbers refer to similar elements throughout the Figures.

FIG. 1 is a schematic top view of a first semiconductor structure in accordance with some embodiments of the present disclosure.

FIG. 2 is a schematic cross-sectional view of the first semiconductor structure along a line A-A′ of FIG. 1 in accordance with some embodiments of the present disclosure.

FIG. 3 is a schematic top view of a second semiconductor structure in accordance with some embodiments of the present disclosure.

FIG. 4 is a schematic cross-sectional view of the second semiconductor structure along a line B-B′ of FIG. 3 in accordance with some embodiments of the present disclosure.

FIG. 5 is a schematic top view of a third semiconductor structure in accordance with some embodiments of the present disclosure.

FIG. 6 is a schematic cross-sectional view of the third semiconductor structure along a line C-C′ of FIG. 5 in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following description of the disclosure accompanies drawings, which are incorporated in and constitute a part of this specification, and illustrate embodiments of the disclosure, but the disclosure is not limited to the embodiments. In addition, the following embodiments can be properly integrated to complete another embodiment.
References to “one embodiment,” “an embodiment,” “exemplary embodiment,” “other embodiments,” “another embodiment,” etc. indicate that the embodiment(s) of the disclosure so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “in the embodiment” does not necessarily refer to the same embodiment, although it may.
As used herein, the term “anti-fuse” refers to a semiconductor device which is a normally open circuit. The anti-fuse can be “blown” to become a short circuit when a programming voltage is applied. In some embodiments of the present disclosure, the anti-fuse structure includes in a gate oxide (GOX) anti-fuse structure.
In order to make the present disclosure completely comprehensible, detailed steps and structures are provided in the following description. Obviously, implementation of the present disclosure does not limit special details known by persons skilled in the art. In addition, known structures and steps are not described in detail, so as not to unnecessarily limit the present disclosure. Preferred embodiments of the present disclosure will be described below in detail. However, in addition to the detailed description, the present disclosure may also be widely implemented in other embodiments. The scope of the present disclosure is not limited to the detailed description, and is defined by the claims.
In a fuse array structure, an antifuse dielectric such as a very thin oxide barrier layer is employed between a pair of conductors. Formation of a conductive channel between the conductors across the antifuse dielectric is performed by a dielectric breakdown of the antifuse dielectric. The antifuse dielectric can be broken down by applying a high voltage pulse across the antifuse dielectric.
With the technological advancement, functionality and capacity of the fuse array structure is increased. However, an overall size of the fuse array structure continues to become smaller and smaller. As such, an isolation distance between the antifuse dielectric and the word line or bit line may not be sufficient for such a high voltage pulse of the dielectric breakdown. As a result, reliability of the fuse array structure is adversely affected.
In the present disclosure, a semiconductor structure is disclosed. The semiconductor structure includes a substrate including a first surface, a first doped region disposed under the first surface, a second doped region disposed under the first surface, and a recess indented into the substrate and disposed between the first doped region and the second doped region; a control gate structure disposed over the first doped region and electrically connected to a control bit line; a fuse gate structure disposed over the second doped region and electrically connected to a fuse bit line; and a buried word line disposed between the control gate structure and the fuse gate structure, wherein the buried word line is disposed within the recess of the substrate. Since the buried word line is buried in the substrate, a distance between the the buried word line and the fuse gate structure can be maximized. Therefore, electrical isolation between the buried word line and the fuse gate structure is improved.
FIG. 1 is a schematic top view of a first semiconductor structure 100 in accordance with some embodiments of the present disclosure. FIG. 2 is a schematic cross-sectional view of the first semiconductor structure 100 along a line A-A′ of FIG. 1.
In some embodiments, the first semiconductor structure 100 is formed adjacent to a memory device such as a dynamic random access memory (DRAM) device or the like. In some embodiments, the first semiconductor structure 100 is a fuse array structure or a part of the fuse array structure.
In some embodiments, the first semiconductor structure 100 includes several conductive lines extending over a substrate 101. In some embodiments, the conductive lines are arranged in rows and columns. In some embodiments, the conductive lines include several bit lines (102, 103) and several word lines 104. In some embodiments, the bit lines (102, 103) are substantially orthogonal to the word lines 104. In some embodiments, the bit lines (102, 103) are electrically isolated from each other. In some embodiments, the word lines 104 are electrically isolated from each other.
In some embodiments, the bit lines include a control bit line 102 and a fuse bit line 103. In some embodiments, information or data can be stored in the memory through the bit line when the gate is opened by the word line. In some embodiments, the control bit line 102 and the fuse bit line 103 are substantially parallel to each other.
In some embodiments, the first semiconductor structure 100 includes the substrate 101. In some embodiments, the substrate 101 is a semiconductive substrate. In some embodiments, the substrate 101 includes semiconductive material such as silicon, germanium, gallium, arsenic, or combinations thereof. In some embodiments, the substrate 101 is a silicon substrate. In some embodiments, the substrate 101 includes material such as ceramic, glass or the like. In some embodiments, the substrate 101 is a silicon on insulator (SOI) substrate, wherein an insulation layer is disposed over a silicon substrate. In some embodiments, the substrate 101 is fabricated with a predetermined functional circuit thereon.
In some embodiments, the substrate 101 includes a first surface 101 a and a second surface 101 b opposite to the first surface dopants. In some embodiments, an active region 101 c (shown in FIG. 1) is disposed over or in the substrate 101. In some embodiments, the active region 101 c is disposed over or proximal to the first surface 101 a of the substrate 101. In some embodiments, the active region 101 c is disposed diagonally over the first surface 101 a of the substrate 101.
In some embodiments, the active region 101 c includes several doped regions (101 d, 101 e) (shown in FIG. 2). In some embodiments, each of the doped regions (101 d, 101 e) includes the same type of dopants. In some embodiments, each of the doped regions (101 d, 101 e) includes a type of dopant that is different from the type of dopant included in the other doped region (101 d, 101 e). In some embodiments, the doped regions (101 d, 101 e) include a first doped region 101 d and a second doped region 101 e. In some embodiments, the first doped region 101 d and the second doped region 101 e are disposed over or under the first surface 101 a of the substrate 101. In some embodiments, the first doped region 101 d and the second doped region 101 e include dopants of the same type. In some embodiments, the first doped region 101 d and the second doped region 101 e include N type dopants. In some embodiments, the first doped region 101 d and the second doped region 101 e are of the same conductive type.
In some embodiments, the substrate 101 includes a recess 101 f indented into the substrate 101 and disposed between the first doped region 101 d and the second doped region 101 e. In some embodiments, the recess 101 f is indented into the substrate 101 from the first surface 101 a towards the second surface 101 b of the substrate 101. In some embodiments, the recess 101 f is disposed under the active region 101 c of the substrate 101. In some embodiments, the recess 101 f is disposed under the first doped region 101 d and the second doped region 101 e.
In some embodiments, the first semiconductor structure 100 includes a control gate structure 105 disposed over the first doped region 101 d and electrically connected to the control bit line 102. In some embodiments, the control gate structure 105 includes a masking layer 105 a, a metallic layer 105 b and a polysilicon layer 105 c. In some embodiments, the metallic layer 105 b is disposed over the polysilicon layer 105 c, and the masking layer 105 a is disposed over the metallic layer 105 b. In some embodiments, the masking layer 105 a includes silicon nitride, nitride or the like. In some embodiments, metallic layer 105 b includes tungsten, titanium element or the like.
In some embodiments, the first semiconductor structure 100 includes a fuse gate structure 106 disposed over the second doped region 101 e and electrically connected to the fuse bit line 103. In some embodiments, the fuse gate structure 106 includes a fuse dielectric 106 a, a masking layer 106 b, a metallic layer 106 c and a polysilicon layer 106 d. In some embodiments, the fuse dielectric 106 a is under the masking layer 106 b, the metallic layer 106 c and the polysilicon layer 106 d. In some embodiments, the masking layer 106 b includes silicon nitride, nitride or the like. In some embodiments, metallic layer 106 c includes tungsten, titanium element or the like. In some embodiments, the fuse dielectric 106 a includes oxide, or metal contained oxide or the like.
In some embodiments, the first semiconductor structure 100 includes a buried word line 104 disposed within the substrate 101. In some embodiments, the buried word line 104 is disposed between the control gate structure 105 and the fuse gate structure 106. In some embodiments, the buried word line 104 is disposed within the recess 101 f of the substrate 101. In some embodiments, the buried word line 104 is disposed under and away from the first surface 101 a of the substrate 101. In some embodiments, the buried word line 104 extends between the first surface 101 a and the second surface 101 b of the substrate 101. In some embodiments, the buried word line 104 is disposed under and away from the first doped region 101 d and the second doped region 101 e.
In some embodiments, the buried word line 104 is configured to control a dielectric breakdown of the fuse dielectric 106 a. In some embodiments, the buried word line 104 includes a conductor 104 a within the recess 101 f. In some embodiments, the conductor 104 a includes tungsten, titanium nitride, tungsten nitride, tantalum nitride, and the combination there of, etc.
In some embodiments, the buried word line 104 is surrounded by an isolation layer 104 b. In some embodiments, the isolation layer 104 b is disposed within the recess 101 f of the substrate 101 and between the substrate 101 and the conductor 104 a. In some embodiments, the isolation layer 104 b includes a first portion 104 b-1 and a second portion 104 b-2. In some embodiments, the first portion 104 b-1 is disposed between the conductor 104 a and the substrate 101. In some embodiments, the second portion 104 b-2 is disposed under the conductor 104 a. In some embodiments, the second portion 104 b-2 surround an end portion of the conductor 104 a. In some embodiments, a thickness of the first portion 104 b-1 is substantially greater than a thickness of the second portion 104 b-2. In some embodiments, the isolation layer 104 b includes high-k (high dielectric constant) dielectric material such as hafnium oxide (HfO2).
In some embodiments, a conductive path across the fuse dielectric 106 a is absent if no breakdown voltage is applied between the buried word line 104 and the first fuse gate structure 106. In other words, a conductive path across the fuse dielectric 106 a is formed when the breakdown voltage is applied between the buried word line 104 and the first fuse gate structure 106. In some embodiments, the fuse dielectric 106 a undergoes a dielectric breakdown process when the breakdown voltage is applied between the buried word line 104 and the first fuse gate structure 106. In some embodiments, the fuse dielectric 106 a is breakable when a voltage bias between the buried word line 104 and the fuse bit line 103 is substantially greater than 5V. In some embodiments, the voltage bias is about 5V to about 6V. In some embodiments, the voltage bias is about 6V to about 10V. In some embodiments, the fuse dielectric 106 a is damaged upon the dielectric breakdown process.
FIG. 3 is a schematic top view of a second semiconductor structure 200 in accordance with some embodiments of the present disclosure. FIG. 4 is a schematic cross-sectional view of the second semiconductor structure 200 along a line B-B′ of FIG. 3. In some embodiments, the second semiconductor structure 200 includes a substrate 201, which is in a configuration similar to the substrate 201 described above or illustrated in FIG. 2.
In some embodiments, the substrate 201 includes a first surface 201 a (shown in FIG. 4), a second surface 201 b opposite to the first surface 201, a first doped region 201 d and a second doped region 201 e, which are in configurations similar to those described above or illustrated in FIG. 2. In some embodiments, the substrate 201 includes a first recess 201 f and a buried word line 204 within the first recess 201 f, which are in configurations similar to those described above or illustrated in FIG. 2.
In some embodiments, the substrate 201 includes a second recess 201 g indented into the substrate 201 and adjacent to the second doped region 201 e. In some embodiments, the second recess 201 g extends from the first surface 201 a towards the second surface 201 b of the substrate 201. In some embodiments, the first recess 201 f and the second recess 201 g are formed separately or simultaneously. In some embodiments, a depth of the second recess 201 g is substantially less than a depth of the first recess 201 f.
In some embodiments, the second semiconductor structure 200 includes a control gate structure 205 disposed over the first doped region 201 d and electrically connected to a control bit line 202. In some embodiments, the control gate structure 205 and the control bit line 202 are in configurations similar to those described above or illustrated in FIG. 2.
In some embodiments, the second semiconductor structure 200 includes a fuse gate structure 210 disposed over the first surface 210 a of the substrate 201 and electrically connected to a fuse bit line 203. In some embodiments, the fuse gate structure 210 includes a masking layer 210 a, a metallic layer 210 b under the masking layer 210 a, and a spacer 210 c adjacent to or surrounding the masking layer 210 a and the metallic layer 210 b.
In some embodiments, the masking layer 210 a includes silicon nitride, nitride or the like. In some embodiments, the metallic layer 210 b includes polycrystalline silicon, titanium nitride, tungsten, or the like. In some embodiments, the second fuse gate structure 210 is electrically connected to the fuse bit line 203 through a contact above the masking layer 210 a. In some embodiments, the fuse dielectric 210 d includes oxide, silicon dioxide, etc. In some embodiments, the spacer 210 c includes nitride, silicon nitride, oxide, etc.
In some embodiments, the metallic layer 210 b is at least partially disposed within the second recess 210 g of the substrate 201. In some embodiments, the metallic layer 210 b is disposed on the fuse dielectric 210 d. In some embodiments, at least a portion of the metallic layer 210 b is disposed under the first surface 201 a of the substrate 201. In some embodiments, the fuse dielectric 210 d is disposed within the second recess 210 g. In some embodiments, the fuse dielectric 210 d is disposed between the metallic layer 210 b and the substrate 201. In some embodiments, the fuse dielectric 210 d is conformal to a sidewall of the second recess 201 g.
In some embodiments, the buried word line 204 is disposed under and away from the fuse dialectric 210 d. In some embodiments, a conductive path across the fuse dielectric 210 d is absent if no breakdown voltage is applied between the second fuse gate structure 210 and the buried word line 204. In other words, a conductive path across the fuse dielectric 210 d is formed when a breakdown voltage is applied between the second fuse gate structure 210 and the buried word line 204.
In some embodiments, the fuse dielectric 210 d undergoes a dielectric breakdown process when the voltage is applied between the second fuse gate structure 210 and the buried word line 204. In some embodiments, the fuse dielectric 210 d is breakable when a voltage bias between the buried word line 204 and the fuse bit line 203 is substantially greater than 2V. In some embodiments, the voltage bias is about 2V to about 4V. In some embodiments, the voltage bias is about 5V to about 10V. In some embodiments, the fuse dielectric 210 d is damaged upon the dielectric breakdown process.
FIG. 5 is a schematic top view of a third semiconductor structure 300 in accordance with some embodiments of the present disclosure. FIG. 6 is a schematic cross-sectional view of the third semiconductor structure 300 along a line C-C′ of FIG. 5. In some embodiments, the third semiconductor structure 300 includes a substrate 301, which is in a configuration similar to the substrate 101, 201 described above or illustrated in FIG. 2 or FIG. 4.
In some embodiments, the substrate 301 includes a first surface 301 a, a second surface 301 b opposite to the first surface 301, a first doped region 301 d, a second doped region 301 e, a first recess 301 f and a second recess 301 g, which are in configurations similar to those described above or illustrated in FIG. 4.
In some embodiments, the third semiconductor structure 300 includes a gate structure 311 disposed over the first doped region 301 d and electrically connected to an electrical ground. In some embodiments, the gate structure 311 is electrically connected to a grounded bit line 312. In some embodiments, the gate structure 311 includes a masking layer 311 a, a metallic layer 311 b and a polysilicon layer 311 c. In some embodiments, the masking layer 311 a is disposed over the metallic layer 311 b, and the metallic layer 311 b is disposed over the polysilicon layer 311 c. In some embodiments, the masking layer 311 a includes silicon nitride, nitride or the like. In some embodiments, the metallic layer 311 b includes tungsten, titanium or the like.
In some embodiments, the third semiconductor structure 300 includes a fuse gate structure 313 disposed over the first surface 301 a of the substrate 301 and electrically connected to a control bit line 302. In some embodiments, the fuse gate structure 313 includes a masking layer 313 a, a metallic layer 313 b under the masking layer 313 a, and a spacer 313 c surrounding the masking layer 313 a and the metallic layer 313 b, which are in configurations similar to the fuse gate structure 210 described above or illustrated in FIG. 4.
In some embodiments, the metallic layer 313 b is at least partially disposed within the second recess 301 g. In some embodiments, the third semiconductor structure 300 includes a fuse dielectric 313 d disposed within the second recess 301 g of the substrate 301. In some embodiments, the fuse dielectric 313 d is disposed under the first surface 301 a of the substrate 301. In some embodiments, the fuse dialetric 313 d is in a configuration similar to the fuse dielectric 210 d described above or illustrated in FIG. 4.
In some embodiments, the third semiconductor structure 300 includes a buried word line 304 disposed between the gate structure 311 and the fuse gate structure 313. In some embodiments, the buried word line 304 is disposed within the first recess 301 f of the substrate 301. In some embodiments, the buried word line 304 is in a configuration similar to the buried word line 304 described above or illustrated in FIG. 4.
In some embodiments, the fuse dielectric 313 d undergoes a dielectric breakdown process when a voltage is applied between the fuse gate structure 313 and the buried word line 304. In some embodiments, the fuse dialectric 313 d is breakable when a voltage bias between the buried word line 304 and the control bit line 302 is substantially greater than 2V. In some embodiments, the voltage bias is about 2V to about 4V. In some embodiments, the voltage bias is about 5V to about 10V.
Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, many of the processes discussed above can be implemented through different methods, replaced by other processes, or a combination thereof.
Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein, may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, and steps.

Claims

What is claimed is:

1. A semiconductor structure, comprising:

a substrate including a first surface, a first doped region disposed under the first surface, a second doped region disposed under the first surface, a first recess indented into the substrate and disposed between the first doped region and the second doped region, and a second recess indented into the substrate and adjacent to the second doped region;

a first gate structure disposed over the first doped region and electrically connected to a first bit line;

a second gate structure disposed over the first surface of the substrate and electrically connected to a second bit line; and

a buried word line disposed within the first recess and disposed between the first gate structure and the second gate structure,

wherein the second gate structure is at least partially disposed within the second recess of the substrate.

2. The semiconductor structure of claim 1, wherein a depth of the second recess is substantially less than a depth of the first recess.

3. The semiconductor structure of claim 1, wherein the second gate structure includes a gate dielectric disposed within the second recess of the substrate.

4. The semiconductor structure of claim 3, wherein the gate dielectric is breakable upon a voltage bias between the buried word line and the second bit line.

5. The semiconductor structure of claim 4, wherein the voltage bias between the buried word line and the second bit line is substantially greater than 2V.

6. The semiconductor structure of claim 1, wherein the buried word line is disposed under and away from the first surface of the substrate.

7. The semiconductor structure of claim 1, wherein the buried word line is disposed under and away from the first doped region and the second doped region.

8. The semiconductor structure of claim 1, wherein the recess extends from the first surface of substrate towards a second surface of the substrate opposite to the first surface.

9. The semiconductor structure of claim 1, wherein the second gate structure includes a fuse dielectric disposed on the second doped region.

10. The semiconductor structure of claim 9, wherein the fuse dielectric is breakable when a voltage bias between the buried word line and the fuse bit line is substantially greater than 5V.

11. The semiconductor structure of claim 9, wherein the buried word line is disposed under and away from the fuse dielectric.

12. The semiconductor structure of claim 9, wherein the fuse dielectric includes oxide or metal contained oxide

13. The semiconductor structure of claim 1, wherein the first doped region and the second doped region are of a same conductive type.

14. The semiconductor structure of claim 1, wherein the buried word line includes a conductor and an isolation layer disposed within the recess and between the substrate and the conductor.

15. The semiconductor structure of claim 14, wherein the isolation layer is disposed conformal to a sidewall of the recess.

16. The semiconductor structure of claim 14, wherein the isolation layer includes a first portion disposed between the conductor and the substrate, and a second portion disposed under the conductor, and wherein a thickness of the first portion is substantially greater than a thickness of the second portion.

14. The semiconductor structure of claim 14, wherein the isolation layer includes high-k (high dielectric constant) dielectric material.

18. The semiconductor structure of claim 1, wherein the control bit line and the fuse bit line are substantially orthogonal to the buried word line.

19. The semiconductor structure of claim 1, wherein the control bit line and the fuse bit line are substantially parallel to each other.