Semiconductor device having alternating insulating layers and method of manufacturing same

Abstract

The present disclosure describes a semiconductor device having alternating insulating layers and a method of manufacturing the same. For example, a semiconductor device (100) includes a semiconductor layer (108), a drain region (110) disposed in the semiconductor layer (108), a source region (114) disposed in the semiconductor layer (108), a channel region (108, 112, 116) disposed between the drain region (110) and the source region (114), a gate (122) disposed over the channel region (108, 112, 116), and first and second insulating layers (118, 120) disposed between the gate electrode (122) and the semiconductor layer (108). Segments of the first insulating layer (118) and segments of the second insulating layer (120) alternate along a first direction perpendicular to a second direction defined between the drain region (110) and the source region (114), each of the segments of the first insulating layer (118) having a first thickness, and each of the segments of the second insulating layer (120) having a second thickness perpendicular to the second direction defined between the drain region (110) and the source region (114). And each of the segments of the second insulating layer (120) has a second thickness greater than the first thickness.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor transistors, and more particularly, but not exclusively, to laterally diffused metal oxide semiconductor (LDMOS) transistors. Background Art

[0002] LDMOS devices are field-effect transistors (FETs) designed specifically for high-power applications. In LDMOS devices, the drain and source have a relatively large separation compared to MOS devices designed for other applications, and lateral diffusion is used to create a well-controlled channel region beneath the gate. The operating performance of LDMOS devices is typically influenced by parameters including, for example, specific on-resistance (Rsp) and breakdown voltage (BV). One design goal for LDMOS devices is to reduce Rsp and increase BV, or at least improve one parameter without adversely affecting the other. Summary of the Invention

[0003] This disclosure describes semiconductor devices with alternating gate insulating layers and methods for fabricating the same. This summary is not an exhaustive overview of the disclosure. Rather, its purpose is to present some examples of the disclosure in a simplified form as a prelude to the more detailed description that is presented later.

[0004] In some examples, a semiconductor device includes a semiconductor layer; a drain region disposed in the semiconductor layer; a source region disposed in the semiconductor layer; a channel region disposed between the drain region and the source region; a gate disposed above the channel region; and a first insulating layer and a second insulating layer disposed between the gate and the semiconductor layer. Segments of the first insulating layer and segments of the second insulating layer alternate along a first direction perpendicular to a second direction defined between the drain region and the source region, each of the segments of the first insulating layer having a first thickness, and each of the segments of the second insulating layer having a second thickness greater than the first thickness.

[0005] In some other examples, a semiconductor device includes a semiconductor layer; a drain region disposed in the semiconductor layer; a source region disposed in the semiconductor layer; a channel region disposed between the drain region and the source region; a gate disposed above the channel region; and a gate dielectric layer and a field dielectric layer disposed between the gate and the semiconductor layer. Segments of the gate dielectric layer and segments of the field dielectric layer alternate along a first direction that is perpendicular to a second direction defined between the drain region and the source region, each of the segments of the gate dielectric layer has a first thickness, and each of the segments of the field dielectric layer has a second thickness that is greater than the first thickness.

[0006] In some additional examples, a method of manufacturing a semiconductor device includes forming a semiconductor layer; forming a drain region in the semiconductor layer; forming a source region in the semiconductor layer; forming a channel region between the drain region and the source region; and forming a first insulating layer and a second insulating layer at least partially along the channel region and between the drain region and the source region. Segments of the first insulating layer and segments of the second insulating layer alternate along a first direction perpendicular to a second direction defined between the drain region and the source region, each of the segments of the first insulating layer having a first thickness, and each of the segments of the second insulating layer having a second thickness greater than the first thickness. The method further includes forming a gate on the first insulating layer and the second insulating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1A is a top view of a semiconductor device according to an example of the present disclosure;

[0008] Figures 1B to 1D yes Figure 1A A cross-sectional view of a semiconductor device;

[0009] Figure 1E yes Figure 1A a three-dimensional view of a portion of a semiconductor device;

[0010] Figure 2A is a top view of a semiconductor device according to another example of the present disclosure;

[0011] Figures 2B to 2D yes Figure 2A A cross-sectional view of a semiconductor device;

[0012] Figure 2E yes Figure 2A a three-dimensional view of a portion of a semiconductor device;

[0013] Figure 3A is a top view of a semiconductor device according to another example of the present disclosure;

[0014] Figures 3B to 3E yes Figure 3A A cross-sectional view of a semiconductor device;

[0015] Figure 3F yes Figure 3A a three-dimensional view of a portion of a semiconductor device;

[0016] Figures 4A-4G is a cross-sectional view of a first process flow for forming a segment of a field dielectric layer of a semiconductor device according to an example of the present disclosure;

[0017] Figures 5A-5G is a cross-sectional view of a second process flow for forming a segment of a field dielectric layer of a semiconductor device according to an example of the present disclosure; and

[0018] Figures 6A-6I is a cross-sectional view of a third process flow for forming a segment of a field dielectric layer of a semiconductor device according to an example of the present disclosure. DETAILED DESCRIPTION

[0019] The present disclosure is described with reference to the accompanying drawings. The components in the figures are not drawn to scale. In fact, the emphasis is on clearly illustrating the overall characteristics and principles of the present disclosure. Many specific details and relationships are set forth with reference to the examples in the figures to provide an understanding of the present disclosure. The figures and examples are not intended to limit the scope of the present disclosure to such examples, and other examples are possible by means of interchanging or modifying at least some of the described or illustrated elements. In addition, where elements of the present disclosure can be partially or completely implemented using known components, certain portions of such components that facilitate understanding of the present disclosure are described, and detailed descriptions of other portions of such components are omitted to avoid obscuring the present disclosure.

[0020] As used herein, terms such as "first" and "second" are used to arbitrarily distinguish between the elements described by such terms. Therefore, these terms in the description and claims are not necessarily intended to indicate a temporal or other prioritization of such elements. In addition, considering the orientations shown in the figures, terms such as "front," "back," "top," "bottom," "above," "below," "vertical," "horizontal," "lateral," "downward," "upward," "upper," "lower," etc. are used to refer to the relative directions or positions of features in a device. For example, "upper" or "topmost" may refer to a feature that is positioned closer to the top of the page than other features. The terms used in this manner are interchangeable where appropriate, such that examples of the technology described herein are capable of operating in orientations other than those shown or otherwise described herein. In the following discussion and claims, the terms "including," "includes," "having," "has," "with," or variations thereof are intended to be inclusive in a manner similar to the term "comprising," and thus should be interpreted to mean, for example, "including, but not limited to..." Furthermore, in some instances, the terms "about," "approximately," or "substantially" preceding a value mean + / - 10%-20% of the stated value. Furthermore, unless otherwise indicated, the order of steps in the specification and claims is not intended to limit the order in which the steps are performed, and thus alternative step orders are appropriately contemplated.

[0021] The various structures disclosed herein can be formed using semiconductor processing techniques. Layers comprising a variety of materials can be formed on a substrate (e.g., a semiconductor wafer) using, for example, deposition techniques (e.g., chemical vapor deposition, physical vapor deposition, atomic layer deposition, spin coating, plating), thermal processing techniques (e.g., oxidation, nitridation, epitaxy), and / or other suitable techniques. Similarly, portions of a layer can be selectively removed using, for example, etching techniques (e.g., plasma (or dry) etching, wet etching), chemical mechanical planarization, and / or other suitable techniques, some of which can be combined with photolithography steps. The conductivity (or resistivity) of a substrate (or region of a substrate) can be controlled by doping techniques using various chemical species (which may also be referred to as dopants, dopant atoms, etc.), including, but not limited to, boron, gallium, indium, arsenic, phosphorus, or antimony. Doping can be performed during the initial formation or growth of the substrate (or epitaxial layer grown on the substrate) by ion implantation or other suitable doping techniques.

[0022] As mentioned above, the operational performance of LDMOS devices is often influenced by a trade-off between the specific on-resistance (Rsp) parameter and the breakdown voltage (BV) parameter. For example, a design approach that seeks to achieve the advantage of higher BV by increasing the device's body area results in the disadvantage of higher Rsp. Similarly, a design approach that seeks to reduce Rsp often comes at the expense of a reduced BV rating. Therefore, an LDMOS design approach that effectively manages this trade-off offers technical advantages.

[0023] Semiconductor devices, such as LDMOS devices, that allow for a relatively large reduction in Rsp without a significant loss in BV rating are described herein. In some instances, this and other technical advantages can be achieved by interleaving or alternating first and second insulating layers of different thicknesses between the gate and the semiconductor layer of the semiconductor device in a first direction (e.g., a channel width direction), the first direction being perpendicular to a second direction (e.g., a channel length direction) defined between the source and drain regions of the semiconductor device. Segments of the first insulating layer having a first thickness are interleaved or alternating with segments of the second insulating layer having a second thickness greater than the first thickness. The first insulating layer having the first thickness may be referred to herein as a gate insulator (e.g., a gate dielectric layer), and the second insulating layer having the second thickness may be referred to herein as a field insulator or a stepped dielectric layer (e.g., a field dielectric layer, a field release layer).

[0024] In some instances, shallow trench isolation (STI) regions (or local oxidation of silicon (LOCOS) regions) are formed in the semiconductor layer in the region where a segment of a first insulating layer having a first thickness is formed. The interlaced STI regions (or LOCOS regions) provide isolation that helps maintain BV (or mitigate electric field effects). The region where a segment of a second insulating layer having a second thickness is formed (e.g., a stepped dielectric region) allows Rsp to be reduced relative to the region where the segment of the first insulating layer and the STI region is formed. Current flows laterally from the drain region to the source region under the gate. For example, since the current flows around the STI region formed in the semiconductor layer, the STI region helps to increase Rsp. However, for example, since the current flows more directly from the drain region to the source region through the stepped dielectric region, the stepped dielectric region (e.g., a region where the STI region is not formed) causes Rsp to decrease.

[0025] In other examples, no STI regions are formed in the semiconductor layer in the region where the segment of the first insulating layer having the first thickness is formed. Thus, the region where the segment of the first insulating layer having the first thickness is formed has a reduced Rsp relative to the stepped dielectric region with increased Rsp. However, such a structure has a lower BV than a structure utilizing STI regions in the region where the segment of the first insulating layer having the first thickness is formed. In other examples, the gate can be recessed in the region where the segment of the first insulating layer having the first thickness is formed (e.g., such that the gate terminates further away from the drain region). This allows for some recovery of the BV relative to a structure without a recessed gate.

[0026] Now refer to Figure 1A , shows a top view of LDMOS device 100. LDMOS device 100 includes a drain region 110, a source region 114, and a gate 122. Along a first direction (direction X, e.g., the channel width direction) along gate 122, alternating regions 113 and 115 exist, the first direction being perpendicular to a second direction (direction Y, e.g., the channel length direction) defined between drain region 110 and source region 114. Region 113 is where a stepped dielectric or field insulator is not formed, and region 115 is where a stepped dielectric or field insulator is formed. In the following description, region 113 will be referred to as a non-stepped dielectric region 113, and region 115 will be referred to as a stepped dielectric region 115.

[0027] Figure 1AEach of regions 113 and 115 having the same width in the first direction (Direction X) is shown as an example only. In other examples, non-stepped dielectric region 113 is wider than stepped dielectric region 115 in the first direction (Direction X). In still other examples, stepped dielectric region 115 is wider than non-stepped dielectric region 113 in the first direction (Direction X). In addition, different ones of non-stepped dielectric region 113 and / or stepped dielectric region 115 may have different widths in the first direction (Direction X), e.g., a first one of non-stepped dielectric regions 113 is wider than a second one of non-stepped dielectric regions 113, or a first one of stepped dielectric regions 115 is wider than a second one of stepped dielectric regions 115, combinations thereof, etc. The following describes Figure 1A Additional features of the LDMOS device 100 are shown, as well as some features not explicitly shown.

[0028] Figure 1B The diagram shows a path across one of the non-stepped dielectric regions 113 in a second direction (direction Y) along Figure 1A A first cross-sectional view of the LDMOS device 100 is shown along a cut line. Figure 1C The cross-step dielectric region 115 is shown along the second direction (direction Y). Figure 1A A second cross-sectional view of the LDMOS device 100 is shown along a cut line. Figure 1D The gate 122 is shown in the first direction (direction X) along the Figure 1A A third cross-sectional view of the LDMOS device 100 is shown along a cut line.

[0029] like Figure 1B As shown, the LDMOS device 100 includes a substrate 102, a first buried layer 104, a second buried layer 106, and a semiconductor layer 108, which is formed, for example, by an epitaxial process in some examples, and is therefore an epitaxial layer 108 in these examples. A drain region 110 and a drain drift region 112 are disposed in the epitaxial layer 108. A well region 116 is also disposed in the epitaxial layer 108, and a source region 114 is disposed in the well region 116. A channel region can be considered to extend across a portion of the epitaxial layer 108 beneath the gate 122 between the drain region 110 and the source region 114.

[0030] In some examples, the substrate 102, the second buried layer 106, the epitaxial layer 108, and the well region 116 have a first conductivity (e.g., one of p-type and n-type), while the first buried layer 104, the drain region 110, the drain drift region 112, and the source region 114 have a second conductivity (e.g., the other of p-type and n-type). Although two buried layers are shown, such as the first buried layer 104 and the second buried layer 106, other examples may include one or the other of the buried layers, or no buried layer at all.

[0031] A first insulating layer 118 having a first thickness (in direction Z) is disposed between gate 122 and underlying portions of drain drift region 112, epitaxial layer 108, and well region 116. First insulating layer 118 may be referred to as a gate dielectric or gate insulator.

[0032] like Figure 1C As shown, a second insulating layer 120 having a second thickness (in direction Z) different from the first thickness is disposed between a portion of the gate 122 and an underlying portion of the drain drift region 112. The second insulating layer 120 may be referred to as a stepped dielectric of a field insulator.

[0033] In some examples, the first thickness of the first insulating layer 118 can be in a range between 3 nanometers (nm) and 15 nm, and the second thickness of the second insulating layer 120 can be in a range between 50 nm and 150 nm. In other examples, the thickness ranges of the first insulating layer 118 and the second insulating layer 120 can be different from the above examples, wherein the thickness of the second insulating layer 120 is greater than the thickness of the first insulating layer 118.

[0034] like Figure 1D As shown, segments of the first insulating layer 118 and the second insulating layer 120 alternate in a first direction (direction X) in the non-stepped dielectric region 113 and the stepped dielectric region 115. Thus, in the stepped dielectric region 115, a portion of the gate 122 is further away from the underlying drain drift region 112 (in direction Z).

[0035] In some examples, the first insulating layer 118 and the second insulating layer 120 are formed of the same material, such as an oxide material. In other examples, the first insulating layer 118 and the second insulating layer 120 are formed of different materials, such as the first insulating layer 118 being an oxide material and the second insulating layer 120 being a nitride material, or a multilayer configuration including an interfacial oxide and a nitride material. In other examples, the first insulating layer 118 and the second insulating layer 120 are different oxide materials, etc.

[0036] The gate 122 is disposed over the first insulating layer 118 and at least a portion of the second insulating layer 120, for example, Figure 1C and1D As shown. In some examples, gate 122 is a polysilicon material. In other examples, gate 122 is a metal or other suitable material. As will be discussed in further detail below, gate 122 can be conformally deposited over at least a portion of first insulating layer 118 and second insulating layer 120 so that gate 122 has a uniform thickness. Figure 1C As shown, the gate 122 extends in the second direction (direction Y) and is only disposed over a portion of the second insulating layer 120. However, in other examples, the gate 122 extends further in the second direction (direction Y) to the edge of the second insulating layer 120 closest to the drain region 110, for example, extending to the beginning of the tapered sidewall of the second insulating layer 120, or covering at least a portion of the tapered sidewall of the second insulating layer 120. In some examples, the gate 122 extends further in the second direction (direction Y) than Figure 1C The gate 122 is terminated further away from the edge of the second insulating layer 120 closest to the drain region 110 .

[0037] Silicide layers 124, 126, and 128 are respectively provided in contact with drain region 110, source region 114, and gate 122. Silicide layers 124, 126, and 128 provide ohmic contact and high conductivity.

[0038] An interlayer dielectric (ILD) 130 is disposed over the structure, and conductive vias 132 , 134 , and 136 are disposed in the ILD 130 to contact the silicide layers 124 , 126 , and 128 , respectively.

[0039] Figure 1E A three-dimensional view of a portion of the LDMOS device 100 is shown. More specifically, Figure 1E It is from Figure 1D A three-dimensional view is shown from the perspective of a portion of the cross-sectional view, in which the ILD 130 is not shown.

[0040] Now refer to Figure 2A , shows a top view of an LDMOS device 200. LDMOS device 200 includes a drain region 210, a source region 214, and a gate 222. Along a first direction (direction X, e.g., the channel width direction) along gate 222, alternating regions 213 and 215 exist, the first direction being perpendicular to a second direction (direction Y, e.g., the channel length direction) defined between drain region 210 and source region 214. Region 213 is where no stepped dielectric or field insulator is formed and where STI regions 238 (in some examples, LOCOS regions) are formed, while region 215 is where a stepped dielectric or field insulator is formed. In the following description, region 213 will be referred to as a non-stepped dielectric region 213, while region 215 will be referred to as a stepped dielectric region 215.

[0041] Figure 2A Each of the regions 213 and 215 having the same width in the first direction (Direction X) is shown as an example only. In other examples, the non-stepped dielectric region 213 is wider than the stepped dielectric region 215 in the first direction (Direction X). In still other examples, the stepped dielectric region 215 is wider than the non-stepped dielectric region 213 in the first direction (Direction X). In addition, different ones of the non-stepped dielectric region 213 and / or the stepped dielectric region 215 can have different widths in the first direction (Direction X), e.g., a first one of the non-stepped dielectric regions 213 is wider than a second one of the non-stepped dielectric regions 213 in the first direction (Direction X), a first one of the stepped dielectric regions 215 is wider than the second one of the stepped dielectric regions 215 in the first direction (Direction X), combinations thereof, etc. The following describes Figure 2A Additional features of the LDMOS device 200 are shown, as well as some features not explicitly shown.

[0042] Figure 2B One of the non-stepped dielectric regions 213 in which one of the STI regions 238 is formed is shown along a second direction (direction Y). Figure 2A A first cross-sectional view of the LDMOS device 200 is shown along a cut line. Figure 2C One of the stepped dielectric regions 215 is shown along the second direction (direction Y). Figure 2A A second cross-sectional view of the LDMOS device 200 is shown along a cut line. Figure 2D The gate 222 is shown in the first direction (direction X) along the Figure 2A A third cross-sectional view of the LDMOS device 200 is shown along a cut line.

[0043] The LDMOS device 200 includes a substrate 202, a first buried layer 204, a second buried layer 206, a semiconductor layer 208 (or an epitaxial layer 208), a drain region 210, a drain drift region 212, a source region 214, a well region 216, a first insulator layer 218, a second insulator layer 220, a gate 222, silicide layers 224, 226, and 228, an ILD 230, and conductive vias 232, 234, and 236, which are similar to the substrate 102, the first buried layer 104, the second buried layer 106, the epitaxial layer 108, the drain region 110, the drain drift region 112, the source region 114, the well region 116, the first insulator layer 118, the second insulator layer 120, the gate 122, the silicide layers 124, 126, and 128, the ILD 130 and conductive vias 132, 134, and 136 are provided in the manner described. The channel region can be considered to extend across a portion of the epitaxial layer 208 beneath the gate 222 between the drain region 210 and the source region 214. While two buried layers are shown, such as the first buried layer 204 and the second buried layer 206, other examples may include one or the other of the buried layers, or no buried layer at all.

[0044] like Figure 2A 、 2B As shown in Figures 2 and 2D, the LDMOS device 200 includes an STI region 238 in the non-stepped dielectric region 213. The STI region 238 is formed of an insulating material, which can be the same as or different from the insulating or dielectric material used for the first insulating layer 218 and / or the second insulating layer 220. The STI region 238 is disposed in the drain drift region 212. The STI region 238 extends in a second direction (direction Y) from a first edge of the drain region 210 toward the well region 216, such that at least a portion of the gate 222 is disposed above at least a portion of the STI region 238.

[0045] Figure 2E A three-dimensional view of a portion of an LDMOS device 200 is shown. More specifically, Figure 2E It is from Figure 2D A three-dimensional view is shown from the perspective of a portion of the cross-sectional view, in which the ILD 230 is not shown.

[0046] Now refer to Figure 3A, shows a top view of an LDMOS device 300. LDMOS device 300 includes a drain region 310, a source region 314, and a gate 322. Alternating regions 313 and 315 exist along a first direction (direction X, e.g., the channel width direction) along gate 322, the first direction being perpendicular to a second direction (direction Y, e.g., the channel length direction) defined between drain region 310 and source region 314. Region 313 is where a stepped dielectric is not formed and where gate 322 is recessed away from drain region 310 in the second direction (direction Y), while region 315 is where a stepped dielectric is formed and where gate 322 is not recessed away from drain region 310. In the following description, region 313 will be referred to as a non-stepped dielectric region 313, while region 315 will be referred to as a stepped dielectric region 315.

[0047] Figure 3A Each of regions 313 and 315 is shown as having the same width in the first direction (Direction X) by way of example only. In other examples, non-stepped dielectric region 313 is wider than stepped dielectric region 315 in the first direction (Direction X). In still other examples, stepped dielectric region 315 is wider than non-stepped dielectric region 313 in the first direction (Direction X). Furthermore, different ones of non-stepped dielectric region 313 and / or stepped dielectric region 315 can have different widths in the first direction (Direction X), e.g., a first one of non-stepped dielectric regions 313 is wider than a second one of non-stepped dielectric regions 313 in the first direction (Direction X), a first one of stepped dielectric regions 315 is wider than a second one of stepped dielectric regions 315 in the first direction (Direction X), combinations thereof, and the like.

[0048] Furthermore, in some examples, the amount by which the gate 322 is recessed in the second direction (direction Y) varies between different ones of the non-stepped dielectric regions 313. Thus, in a first one of the non-stepped dielectric regions 313, the gate 322 may be recessed a first distance in the second direction (direction Y) away from the drain region 310, while in a second one of the non-stepped dielectric regions 313, the gate 322 may be recessed a second distance in the second direction (direction Y) away from the drain region 310, where the second distance is different from the first distance.

[0049] In addition, although Figure 3AThe recess of gate 322 is shown aligned relative to the top and bottom boundaries between non-stepped dielectric region 313 and stepped dielectric region 315 in a first direction (direction X, e.g., width direction), but in other examples, the recess in one or more of the non-stepped dielectric regions 313 may be larger or smaller than the width of the non-stepped dielectric region 313, e.g., by design. Furthermore, even when the width of the recess is substantially the same as the width of the non-stepped dielectric region 313, one boundary (e.g., the top boundary) may be covered by gate 322 while the other boundary (e.g., the bottom boundary) may not be covered by gate 322, e.g., due to process non-uniformities / defects resulting in an offset (e.g., a vertical offset of gate 322 relative to an already existing boundary). This is described below. Figure 3A Additional features of the LDMOS device 300 are shown, as well as some features not explicitly shown.

[0050] Figure 3B The diagram shows a path across one of the non-stepped dielectric regions 313 in a second direction (direction Y) along Figure 3A The first cross-sectional view of the LDMOS device 300 is shown along a cut line, wherein the gate 322 is recessed in a second direction (direction Y) away from the drain region 310 . Figure 3C One of the stepped dielectric regions 315 is shown along the second direction (direction Y). Figure 3A A second cross-sectional view of the LDMOS device 300 is shown along the cut line. Figure 3B and 3C As shown, the distance D1 between the drain region 310 and the gate 322 in the non-stepped dielectric region 313 is greater than the distance D2 between the drain region 310 and the gate 322 in the stepped dielectric region 315 . Figure 3D It shows that the gate 322 is along the first direction (direction X) along Figure 3A The third cross-sectional view of the LDMOS device 300 taken along the cut line shown shows that a portion of the gate 322 is recessed away from the drain region 310 in the second direction (direction Y). Figure 3D The absence of gate 322 in the corresponding non-stepped dielectric region 313 is shown. Figure 3E It shows that the gate 322 is along the first direction (direction X) along Figure 3A A fourth cross-sectional view of the LDMOS device 300 is shown taken along a cut line, wherein the gate 322 is continuous (eg, not recessed along the cut line) away from the drain region 310 in the second direction (direction Y).

[0051] The LDMOS device 300 includes a substrate 302, a first buried layer 304, a second buried layer 306, a semiconductor layer 308 (or an epitaxial layer 308), a drain region 310, a drain drift region 312, a source region 314, a well region 316, a first insulator layer 318, a second insulator layer 320, a gate 322, silicide layers 324, 326, and 328, an ILD 330, and conductive vias 332, 334, and 336, which are similar to the substrate 102, the first buried layer 104, the second buried layer 106, the epitaxial layer 108, the drain region 110, the drain drift region 112, the source region 114, the well region 116, the first insulator layer 118, the second insulator layer 120, the gate 122, the silicide layers 124, 126, and 128, the ILD 130 and conductive vias 132, 134 and 136 are arranged in the same manner as described above, except for gate 322. Figure 3A 、 3C , 3D, and 3E, the gate 322 is recessed in the second direction (direction Y) away from the drain region 310 in the non-stepped dielectric region 313, but is not recessed in the stepped dielectric region 315. The channel region can be considered to extend across a portion of the epitaxial layer 308 beneath the gate 322 between the drain region 310 and the source region 314. While two buried layers are shown, such as the first buried layer 304 and the second buried layer 306, other examples may include one or the other of the buried layers, or no buried layer at all.

[0052] In addition, if Figure 3D and 3E As shown in the example of FIG, the gate 322 in the stepped dielectric region 315 terminates at the upper surface of the corresponding segment of the second insulating layer 320. In other examples, the gate 322 can terminate elsewhere on the upper surface, at the edge of the upper surface, or along the tapered sidewall of the corresponding segment of the second insulating layer 320.

[0053] Figure 3F A three-dimensional view of a portion of an LDMOS device 300 is shown. More specifically, Figure 3F It is from Figure 3E A three-dimensional view is shown from the perspective of a portion of the cross-sectional view, in which the ILD 330 is not shown.

[0054] Now about Figures 4A-6I A process flow for forming a stepped dielectric or field insulator (eg, second insulator layer 120 , second insulator layer 220 , or second insulator layer 320 ) is described.

[0055] Figure 4AA cross-sectional view of a structure 400 is shown, which includes a substrate 402, a first buried layer 404, a second buried layer 406, and a semiconductor layer 408 (or epitaxial layer 408), which are similar to the substrates 102, 202, and 302, the first buried layers 104, 204, and 304, the second buried layers 106, 206, and 306, and the epitaxial layers 108, 208, and 308 described above with respect to the LDMOS devices 100, 200, and 300, respectively. As shown, an insulator layer 420 is blanket deposited over the epitaxial layer 408, wherein the insulator layer 420 will be patterned later so that the insulator layer 420 in the non-stepped dielectric region 413 (e.g., Figure 4D ), and retain the insulator layer 420 in the stepped dielectric region 415 (as shown Figure 4D As shown), the non-stepped dielectric region and the stepped dielectric region are arranged in a first direction ( Figure 4D 4. The insulator layer 420 may have a thickness (in the direction Z) similar to that of the second insulating layer 120 of the LDMOS device 100. In the following description, it is assumed that the substrate 402, the second buried layer 406, and the epitaxial layer 408 are of p-type conductivity, and the first buried layer 404 is of n-type conductivity. Therefore, in the following description, the substrate 402 may be referred to as a p-type substrate 402, the first buried layer 404 may be referred to as an n-type buried layer (NBL) 404, the second buried layer 406 may be referred to as a p-type buried layer (PBL) 406, and the epitaxial layer 408 may be referred to as a lightly doped p-type epitaxial layer 408. In other examples, the conductivity may be reversed.

[0056] To form the NBL 404, a lightly doped p-type epitaxial layer 408 is grown on the p-type substrate 402, and a portion of the lightly doped p-type epitaxial layer 408 is processed (e.g., by dopant implantation) to form the NBL 404. The lightly doped p-type epitaxial layer 408 serves as the body region of the LDMOS device and may therefore be referred to as the body region 408. Both the p-type substrate 402 and the lightly doped p-type epitaxial layer 408 may comprise silicon, and may also comprise other materials. The PBL 406 is formed using a high energy p-type implant to add dopant to a portion of the lightly doped p-type epitaxial layer 408. The p-type implant may be boron at a dose of 1×10 12 cm -2 to 1×10 13 cm -2, with an energy of 400 keV to 3 mega-electron volts (MeV). Indium may also be used as the implant species. For low voltage (e.g., 20V) versions of the LDMOS transistor, the p-type implant used to form the PBL 406 may be a blanket implant, while for higher voltage (e.g., >30V) versions of the LDMOS device, the p-type implant used to form the PBL 406 may be a masked implant that allows for selective placement. For the masked implant, a photomask (not specifically shown) is deposited and patterned to have openings that expose regions of the lightly doped p-type epitaxial layer 408 in which the p-type implant is performed to form the PBL 406 (e.g., a localized PBL 406). Although Figures 4A-4G 4. NBL 404 and PBL 406 are shown, but are optional for constructing an LDMOS device (eg, an example may include both one or the other of the buried layers as shown, or no buried layer at all).

[0057] An insulator layer 420 is blanket deposited over the lightly doped p-type epitaxial layer 408. The insulator layer 420 is a dielectric material such as an oxide material. Figure 4B As shown, a mask layer 421 may be blanket deposited over the insulator layer 420. In some examples, the mask layer 421 is formed of a photosensitive organic material. Figure 4C and 4D As shown, the mask layer 421 is patterned to cover the portion of the insulator layer 420 where the stepped dielectric or field insulator is to be formed. Figure 4D As shown, this includes patterning mask layer 421 such that mask layer 421 remains in stepped dielectric region 415 and mask layer 421 is removed in non-stepped dielectric region 413 .

[0058] like Figure 4E As shown, a suitable etching process is then used to remove the portion of the insulator layer 420 exposed by the patterned mask layer 421. Figure 4F As shown, the remaining portion of the insulator layer 420 is then further etched to form a tapered sidewall. In other examples, Figure 4E The tapered sidewalls of the insulator layer 420 are formed in the same etching process of FIG.

[0059] Then, if Figure 4G As shown, the patterned mask layer 421 is removed, resulting in sections of the insulator layer 420 in stepped dielectric regions 415 alternating with non-stepped dielectric regions 413 in a first direction (direction X). The sections of the insulator layer 420 correspond to the stepped dielectric sections of the insulating layers 120, 220, and 320 described above with respect to the LDMOS devices 100, 200, and 300, respectively. It should be noted that due to Figures 4A-4GThe focus is on forming the insulator layer 420 in the stepped dielectric region 415, and thus the insulator layer 420 formed in the non-stepped dielectric region 413 is not explicitly shown. Figure 1D The first insulating layer 118 is similar to a gate dielectric or gate insulator layer.

[0060] Figure 5A A cross-sectional view of structure 500 is shown, which includes a substrate 502, a first buried layer 504, a second buried layer 506, and an epitaxial layer 508, which are similar to the substrates 102, 202, and 302, first buried layers 104, 204, and 304, second buried layers 106, 206, and 306, and epitaxial layers 108, 208, and 308 described above with respect to LDMOS devices 100, 200, and 300, respectively. An interfacial oxide layer 519 is blanket deposited over epitaxial layer 508, followed by a blanket deposition of a nitride-based insulator layer 520 over interfacial oxide layer 519. Interfacial oxide layer 519 is a thin layer that helps nitride-based insulator layer 520 adhere to underlying structures (or relieves stress between nitride-based insulator layer 520 and epitaxial layer 508). The nitride-based insulator layer 520 is patterned so that the nitride-based insulator layer 520 in the non-stepped dielectric region 513 (eg, Figure 5D ), and retaining the nitride-based insulator layer 520 in the stepped dielectric region 515 (as shown Figure 5D As shown), the non-stepped dielectric region and the stepped dielectric region are arranged in a first direction ( Figure 5D In the following description, it is assumed that the substrate 502, the second buried layer 506, and the epitaxial layer 508 are of p-type conductivity, and the first buried layer 504 is of n-type conductivity. Therefore, in the following description, the substrate 502 may be referred to as a p-type substrate 502, the first buried layer 504 may be referred to as an NBL 504, the second buried layer 506 may be referred to as a PBL 506, and the epitaxial layer 508 may be referred to as a lightly doped p-type epitaxial layer 508. In other examples, the conductivity may be reversed.

[0061] NBL 504, PBL 506, and lightly doped p-type epitaxial layer 508 are formed in a manner similar to that described above with respect to NBL 404, PBL 406, and lightly doped p-type epitaxial layer 408. Like NBL 404 and PBL 406, NBL 504 and PBL 506 are optional layers (e.g., examples may include both, one or the other of the buried layers as shown, or no buried layer at all).

[0062] Interfacial oxide layer 519 is an oxide material blanket deposited over lightly doped p-type epitaxial layer 508. Nitride-based insulator layer 520 is blanket deposited over interfacial oxide layer 519 and may have a similar thickness (in direction Z) as insulator layer 420. Nitride-based insulator layer 520 is a nitride material.

[0063] like Figure 5B As shown, a mask layer 521 may be blanket deposited over the nitride-based insulator layer 520. The mask layer 521 is formed of a material similar to the mask layer 421. Figure 5C and 5D As shown, the mask layer 521 is patterned to cover the portion of the nitride-based insulator layer 520 where the stepped dielectric or field insulator is to be formed. Figure 5D As shown, this includes patterning mask layer 521 such that mask layer 521 remains in stepped dielectric region 515 and mask layer 521 is removed in non-stepped dielectric region 513 .

[0064] like Figure 5E As shown, the portions of the nitride-based insulator layer 520 exposed by the patterned mask layer 521 are then removed using a suitable etching process.

[0065] like Figure 5F As shown, the remaining portion of the nitride-based insulator layer 520 is then further etched to form a tapered sidewall. Figure 5G As shown, the patterned mask layer 521 is removed, resulting in sections of the nitride-based insulator layer 520 in stepped dielectric regions 515 alternating with non-stepped dielectric regions 513 in a first direction (direction X). The sections of the nitride-based insulator layer 520 correspond to the stepped dielectric sections of the insulating layers 120, 220, and 320 described above with respect to the LDMOS devices 100, 200, and 300, respectively. It should be noted that due to Figures 5A-5G The focus is on forming the nitride-based insulator layer 520 in the stepped dielectric region 515, and thus the formation of the nitride-based insulator layer 520 in the non-stepped dielectric region 513 is not explicitly shown. Figure 1D The first insulating layer 118 is similar to a gate dielectric or gate insulator layer.

[0066] Figure 6AA cross-sectional view of a structure 600 is shown, which includes a substrate 602, a first buried layer 604, a second buried layer 606, and an epitaxial layer 608, which are similar to the substrates 102, 202, and 302, the first buried layers 104, 204, and 304, the second buried layers 106, 206, and 306, and the epitaxial layers 108, 208, and 308 described above with respect to the LDMOS devices 100, 200, and 300, respectively. In the following description, it is assumed that the substrate 602, the second buried layer 606, and the epitaxial layer 608 are of p-type conductivity, and the first buried layer 604 is of n-type conductivity. Therefore, in the following description, the substrate 602 may be referred to as a p-type substrate 602, the first buried layer 604 may be referred to as an NBL 604, the second buried layer 606 may be referred to as a PBL 606, and the epitaxial layer 608 may be referred to as a lightly doped p-type epitaxial layer 608. In other examples, the conductivity may be reversed.

[0067] NBL 604, PBL 606, and lightly doped p-type epitaxial layer 608 are formed in a manner similar to that described above with respect to NBL 404, PBL 406, and lightly doped p-type epitaxial layer 408. Like NBL 404 and PBL 406, NBL 604 and PBL 606 are optional layers (e.g., examples may include both, one or the other of the buried layers as shown, or no buried layer at all).

[0068] like Figure 6A As shown, a nitride layer 621 is blanket deposited over the lightly doped p-type epitaxial layer 608. The thickness of the nitride layer 621 (in the direction Z) corresponds to the desired thickness of the resulting stepped dielectric or field insulator to be formed. Figure 6B As shown, a mask layer 623 (eg, a photomask) is formed over the nitride layer 621 .

[0069] like Figure 6C and 6D As shown, the mask layer 623 is patterned to expose portions of the nitride layer 621 where the stepped dielectric or field insulator is to be formed. Figure 6D It is shown how the mask layer 623 is patterned in a first direction (direction X) so as to enable the formation of alternating non-stepped dielectric regions 613 and stepped dielectric regions 615 .

[0070] like Figure 6E As shown, a suitable etching process is then used to remove the portion of the nitride layer 621 exposed by the patterned mask layer 623. Figure 6F As shown, the patterned mask layer 623 is then removed. Figure 6G As shown, an epitaxial layer 625 is then selectively grown over the portion of the lightly doped p-type epitaxial layer 608 exposed by the patterned nitride layer 621. Figure 6HAs shown, the epitaxial layer 625 is then subjected to an oxidation process to form the insulator layer 620. Figure 6I As shown, the nitride layer 621 is then removed. Although not shown, the insulator layer 620 can be subjected to further etching to form tapered sidewalls. The sections of the insulator layer 620 correspond to the stepped dielectric sections of the insulating layers 120, 220, and 320 described above with respect to the LDMOS devices 100, 200, and 300, respectively. Note that due to Figures 6A-6I The focus is on forming the insulator layer 620 in the stepped dielectric region 615, and thus the insulator layer 620 formed in the non-stepped dielectric region 613 is not explicitly shown. Figure 1D The first insulating layer 118 is similar to a gate dielectric or gate insulator layer.

[0071] form Figure 4G 、 5G The processing steps for the stepped dielectric sections shown in FIG6I (hereinafter referred to as a stepped dielectric process module) can be integrated with other processing steps to form additional portions of the LDMOS device, thereby forming one of the LDMOS devices 100, 200, and 300 described above. In some examples, the STI regions (e.g., including the reference MOSFET) can be formed. Figures 2A to 2E The step-type dielectric process module is added after the STI region 238 described above. Subsequently, additional processing steps may be performed, such as forming a drain drift region (e.g., drain drift region 112, drain drift region 212, or drain drift region 312), forming a well region (e.g., well region 116, well region 216, or well region 316), forming a gate insulator (e.g., first insulator layer 118, first insulator layer 218, or first insulator layer 318), forming a gate (e.g., gate 122, gate 222, or gate 322), and forming a gate. 2), forming gate spacers (not specifically shown), forming a drain region (e.g., drain region 110, drain region 210, or drain region 310) and a source region (e.g., source region 114, source region 214, or source region 314), forming a silicide layer (e.g., silicide layers 124, 126, and 128, silicide layers 224, 226, and 228, or silicide layers 324, 326, and 328), forming an ILD (e.g., ILD 130, ILD 230, or ILD 330), and forming conductive vias (e.g., conductive vias 132, 134, and 136, conductive vias 232, 234, and 236, or conductive vias 332, 334, and 336).

[0072] In other instances, a stepped dielectric process module can be added after forming the STI regions and additional implants to form various drift and well regions in the semiconductor layer (e.g., epitaxial layers 108, 208, 308) before forming a gate insulator (e.g., first insulator layer 118, first insulator layer 218, or first insulator layer 318) and a gate (e.g., gate 122, gate 222, or gate 322) on the gate insulator. After forming the gate stack including the gate insulator and the gate, additional process steps may be performed, such as forming gate spacers (not specifically shown), forming drain regions (e.g., drain region 110, drain region 210, or drain region 310) and source regions (e.g., source region 114, source region 214, or source region 314), forming silicide layers (e.g., silicide layers 124, 126, and 128, silicide layers 224, 226, and 228, or silicide layers 324, 326, and 328), forming an ILD (e.g., ILD 130, ILD 230, or ILD 330), and forming conductive vias (e.g., conductive vias 132, 134, and 136, conductive vias 232, 234, and 236, or conductive vias 332, 334, and 336). Certain aspects of the process flow for forming such additional portions will now be described.

[0073] In some examples, a drain drift region (e.g., drain drift region 112, drain drift region 212, or drain drift region 312) is formed in a semiconductor layer (e.g., epitaxial layer 108, epitaxial layer 208, or epitaxial layer 308) by performing one or more mask implantation steps, such as by forming a drain drift mask layer (or photomask). In some examples, the implantation to form the drain drift region is performed in two steps (e.g., a first implantation process using a first energy and a first dose, followed by a second implantation process using a second energy and a second dose). In some examples, the first implantation process is performed at a first energy of 20-40 kiloelectronvolts (keV) and a second implantation process of 2-8×10 12 cm -2 In some examples, for an oxide thickness of 70-110 nanometers (nm), the first implantation process implants the phosphorus dopant at a first energy of 20-40 keV. In some examples, the first dose is 2-5×10 12 cm -2 The second implantation process uses the same drain drift mask layer to implant the same region of the semiconductor layer. In some examples, the second energy is greater than the first energy. In some examples, the second implantation process is performed at a second energy of 70-350 keV and a current of 2-5×10 12 cm -2The second implant process implants the phosphorus dopant at a second dose of 100 keV. In some examples, the second implant process implants the phosphorus dopant at a second energy of less than or equal to 150 keV. In some examples, the second implant process implants the phosphorus dopant at a second energy of greater than or equal to 100 keV (e.g., 100-350 keV). In some examples, the second implant process includes more than one implant, such as an implant performed at 120 keV and another implant performed at 250 keV.

[0074] After forming the drain drift region, the drain drift mask layer is removed and the well region mask layer is patterned over the semiconductor layer to expose a portion of the semiconductor layer where the well region (e.g., well region 116, well region 216, or well region 316) is to be formed. An implantation process is then performed to implant p-type dopants into the exposed region of the semiconductor layer to form a well region. The p-type dopant may include boron. In addition to boron, the p-type dopant may also include indium. Indium is a relatively large atom and has the advantage of a low diffusion coefficient relative to boron. In the case of boron implantation, the dose used in the implantation process is sufficient to laterally form a channel and suppress the body NPN effect during operation of the LDMOS device. For example, an energy of 20 keV and a dose of 8×10 13 cm -2 to 3.0×10 14 cm -2 (For example, 1.5×10 14 cm 2 ), boron implantation with an inclination angle of less than 5 degrees (eg, 2 degrees). The well region mask layer can then be removed after the implantation process.

[0075] A gate insulator (e.g., first insulating layer 118, first insulating layer 218, or first insulating layer 318) and a gate (e.g., gate 122, gate 222, or gate 322) can be formed on the structure by deposition and patterning using one or more gate mask layers. In some instances, the gate insulator material is formed using a high temperature furnace operation or rapid thermal processing. The gate insulator material can have a thickness in the range of approximately 3 nm to 15 nm. The gate material is then deposited over the gate insulator. In some instances, the gate material is deposited using a gate deposition process using any of a variety of silane-based precursors. Polysilicon is an example of a gate material, however, a metal gate or CMOS-based replacement gate process can also be used to form the gate.

[0076] After depositing the gate insulator material and the gate material, a gate mask layer may be formed over the gate material and the underlying gate insulator material, where the final gate and gate insulator should remain. Portions of the gate insulator material and gate material exposed by the one or more gate mask layers are then removed (e.g., using plasma etching or other suitable etching processes) to define the final gate and gate insulator, and then the one or more gate mask layers are removed. In the non-stepped dielectric region (e.g., Figure 4D In the example where the gate is recessed in the region 413 shown in FIG. 4 , the gate mask layer is appropriately patterned in the first direction (direction X) to achieve the desired recess of the gate in such a region. In some examples, a lightly doped drain region is formed after patterning the gate, for example, by implanting an n-type dopant species that is self-aligned at the edge of the patterned gate. Subsequently, gate spacers may be formed on the sidewalls of the patterned gate.

[0077] In some examples, after forming the gate spacers, a drain / source mask layer may be formed to expose portions of the drain drift region (e.g., drain drift region 112, drain drift region 212, or drain drift region 312) and the well region (e.g., well region 116, well region 216, or well region 316), where the drain region (e.g., drain region 110, drain region 210, or drain region 310) and the source region (e.g., source region 114, source region 214, or source region 314) will be formed, respectively. An implantation process is then performed to implant n-type dopants into the exposed regions of the drain drift region and the well region to form the drain and source regions. The drain / source mask layer is then removed.

[0078] After forming the source and drain regions, a silicide layer (e.g., silicide layers 124, 126, and 128, silicide layers 224, 226, and 228, or silicide layers 324, 326, and 328) is then formed over the drain, source, and gate regions. In some examples, the silicide layer is formed by forming a metal layer that forms a metal silicide at a temperature consistent with silicon processing conditions, and then heating the structure to form the metal silicide. Unreacted portions of the metal layer are then removed, for example, using a wet stripping process.

[0079] An ILD (e.g., ILD 130, ILD 230, or ILD 330) is then deposited on the structure. The ILD is formed of a dielectric material. A contact mask layer is then formed over the ILD to expose areas where conductive vias (e.g., conductive vias 132, 134, and 136, conductive vias 232, 234, and 236, or conductive vias 332, 334, and 336) are to be formed in the ILD. The exposed areas of the ILD are then removed, followed by filling the conductive vias, and the contact mask layer is then removed. The conductive vias are formed of a suitable metal such as tungsten. Additional metal interconnects may be formed as needed to construct a metal interconnect system for the structure.

[0080] In instances where STI regions (eg, STI regions 238) are to be formed, the STI regions 238 may be formed prior to forming the stepped dielectric or field insulator (eg, prior to forming the stepped dielectric or field insulator). Figure 4A Before forming the insulator layer 420 in Figure 5A Before forming the interface oxide layer 519, or before forming Figure 6A STI regions are formed before the nitride layer 621 in the semiconductor layer is formed. To this end, an STI mask layer is formed over the semiconductor layer (e.g., the lightly doped p-type epitaxial layer 408, 508, or 608), and then the portion of the p-type epitaxial layer exposed by the STI mask layer is removed, and an STI material is deposited to form the STI regions.

[0081] Although Figures 4A-4G , 5A-5G and 6A-6I show a process flow for forming a stepped dielectric or field insulator before forming a drain region (e.g., drain region 110, drain region 210 or drain region 310), a drain drift region (e.g., drain drift region 112, drain drift region 212 or drain drift region 312), a source region (e.g., source region 114, source region 214 or source region 314) and a well region (e.g., well region 116, well region 216 or well region 316), but this is only an example.

[0082] In other examples, a stepped dielectric or field insulator may be formed after forming the drain region, drain drift region, source region, and well region. Figures 4A-6I Various other types of processes than those shown can be used to form the stepped dielectric or field insulator. In some examples, the stepped dielectric or field insulator is thermally grown using a local oxidation of silicon (LOCOS) process to form a silicon dioxide layer with tapered ends over a silicon layer (e.g., epitaxial layer 108, epitaxial layer 208, or epitaxial layer 308).

[0083] In addition, although various features or components have been shown with specific arrangements or configurations according to the illustrated embodiments, other arrangements and configurations are possible. Furthermore, aspects of the present technology described in the context of the exemplary embodiments may also be combined or eliminated in other embodiments. Therefore, the breadth and scope of this specification is not limited by any of the embodiments described above.

Claims

1. A semiconductor device comprising: semiconductor layer; a drain region disposed in the semiconductor layer; a source region disposed in the semiconductor layer; a channel region disposed between the drain region and the source region; a gate disposed above the channel region; as well as A first insulating layer and a second insulating layer are arranged between the gate and the semiconductor layer, wherein segments of the first insulating layer and segments of the second insulating layer alternate along a first direction, the first direction is perpendicular to a second direction defined between the drain region and the source region, each of the segments of the first insulating layer has a first thickness, and each of the segments of the second insulating layer has a second thickness greater than the first thickness. The semiconductor device according to claim 1 , wherein the second insulating layer comprises an oxide material. The semiconductor device according to claim 1 , wherein the second insulating layer comprises a nitride material. The semiconductor device of claim 1 , wherein each of the segments of the second insulating layer comprises a tapered sidewall.

5. The semiconductor device according to claim 1 , further comprising: A trench isolation segment is disposed in the semiconductor layer and aligned with the segment of the first insulation layer in the first direction. The semiconductor device according to claim 5 , wherein the trench isolation region comprises a shallow trench isolation region. 7 . The semiconductor device according to claim 1 , wherein the gate comprises a recessed portion aligned with the section of the first insulating layer. 8 . The semiconductor device according to claim 7 , wherein the recessed portion extends in the second direction. 9 . The semiconductor device according to claim 1 , wherein the semiconductor device comprises a laterally diffused metal oxide semiconductor (LDMOS) transistor.

10. A semiconductor device comprising: semiconductor layer; a drain region disposed in the semiconductor layer; a source region disposed in the semiconductor layer; a channel region disposed between the drain region and the source region; a gate disposed above the channel region; as well as a gate dielectric layer and a field dielectric layer disposed between the gate and the semiconductor layer, wherein segments of the gate dielectric layer and segments of the field dielectric layer alternate along a first direction perpendicular to a second direction defined between the drain region and the source region, each of the segments of the gate dielectric layer having a first thickness, and each of the segments of the field dielectric layer having a second thickness greater than the first thickness. The semiconductor device according to claim 10 , wherein the field dielectric layer comprises an oxide material. The semiconductor device according to claim 10 , wherein the field dielectric layer comprises a nitride material. 13 . The semiconductor device of claim 10 , wherein each of the segments of the field dielectric layer comprises a tapered sidewall.

14. The semiconductor device according to claim 10, further comprising: A trench isolation segment is disposed in the semiconductor layer and aligned with the segment of the gate dielectric layer in the first direction. 15 . The semiconductor device according to claim 10 , wherein the gate comprises a recessed portion aligned with the segment of the gate dielectric layer and extending in the second direction. 16 . The semiconductor device according to claim 10 , wherein the semiconductor device comprises a laterally diffused metal oxide semiconductor (LDMOS) transistor.

17. A method of manufacturing a semiconductor device, comprising: forming a semiconductor layer; forming a drain region in the semiconductor layer; forming a source region in the semiconductor layer; forming a channel region between the drain region and the source region; forming a first insulating layer and a second insulating layer at least partially along the channel region and between the drain region and the source region, wherein segments of the first insulating layer and segments of the second insulating layer alternate along a first direction that is perpendicular to a second direction defined between the drain region and the source region, each of the segments of the first insulating layer having a first thickness, and each of the segments of the second insulating layer having a second thickness greater than the first thickness; as well as A gate is formed on the first insulating layer and the second insulating layer.

18. The method of claim 17, wherein the second insulating layer is an oxide material, and wherein forming the second insulating layer comprises: forming an oxide layer over the semiconductor layer; forming a mask layer over the oxide layer; patterning the mask layer to cover a portion of the oxide layer where the section of the second insulating layer will be formed; removing an exposed portion of the oxide layer; as well as The mask layer is removed.

19. The method of claim 17, wherein the second insulating layer is an oxide material, and wherein forming the second insulating layer comprises: forming a nitride layer over the semiconductor layer; forming a mask layer over the nitride layer; patterning the mask layer to expose a portion of the nitride layer where the section of the second insulating layer will be formed; removing the exposed portion of the nitride layer to expose the surface of the semiconductor layer; removing the mask layer; growing an epitaxial layer over the exposed surface of the semiconductor layer; oxidizing the epitaxial layer; as well as Remaining portions of the nitride layer are removed.

20. The method of claim 17, wherein the second insulating layer is a nitride material, and wherein forming the second insulating layer comprises: forming an interfacial oxide layer above the semiconductor layer; forming a nitride layer over the interface oxide layer; forming a mask layer over the nitride layer; patterning the mask layer to cover a portion of the nitride layer where the section of the second insulating layer is to be formed; removing an exposed portion of the nitride layer; as well as The mask layer is removed.

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