Abstract: A semiconductor fuse box includes a fuse structure and a protective structure disposed between the fuse structure and an integrated circuit structure. The protective structure has at least one irregular side surface. The protective structure (which may also include a pad formed there-under) extends beyond a bottom of the fuse structure. Such an irregular side surface and such an extension of the protective structure minimize propagation of damaging energy to the adjacent integrated circuit structure when a laser beam is directed to the fuse structure.

Abstract: A programmable anti-fuse element includes a substrate (224), an N-well (426) in the substrate, an electrically insulating layer (427) over the N-well, and a gate electrode (430) over the electrically insulating layer. The gate electrode has n-type doping so that the N-well is able to substantially contain within its boundaries a current generated following a programming event of the programmable anti-fuse element. In the same or another embodiment, a twice-programmable fuse element (100) includes a metal gate fuse (110) and an oxide anti-fuse (120) such as the programmable anti-fuse element just described.

Abstract: The present invention discloses a semiconductor device, the device comprising a semiconductor layer on a substrate. A gate oxide and a gate electrode are formed on the semiconductor substrate. A gate conductive layer is formed on the gate electrode. A first doped region is formed in the semiconductor layer. A dielectric spacer is optionally formed onto the sidewall of the gate electrode and part of the semiconductor layer. A second doped region is formed from a predetermined distance to the gate electrode, wherein the predetermined distance is no less than the distance between the first doped region and the gate electrode. A third doped region is formed adjacent to the first doped region in the semiconductor layer and between the first doped region and the second doped region.

Abstract: The present invention provides an electrical fuse structure for achieving a post-programming resistance distribution with higher resistance values and to enhance the reliability of electrical fuse programming. A partly doped electrical fuse structure with undoped semiconductor material in the cathode combined with P-doped semiconductor material in the fuselink and anode is disclosed and the data supporting the superior performance of the disclosed electrical fuse is shown.

Abstract: An antifuse circuit includes a terminal, an antifuse transistor, and a bias transistor. The antifuse transistor is formed on a substrate. The antifuse transistor is coupled to the terminal and includes a first gate terminal coupled to receive a first select signal. The bias transistor is coupled between the substrate and a bias voltage terminal. The bias transistor has a second gate terminal and is operable to couple the bias voltage terminal to the substrate responsive to an assertion of a bias enable signal at the second gate terminal.

Abstract: The present invention provides structures for an integrated antifuse that incorporates an integrated sensing transistor with an integrated heater. Two terminals connected to the upper plate allow the heating of the upper plate, accelerating the breakdown of the antifuse dielectric at a lower bias voltage. Part of the upper plate also serves as the gate of the integrated sensing transistor. The antifuse dielectric serves as the gate dielectric of the integrated transistor. The lower plate comprises a channel, a drain, and a source of a transistor. While intact, the integrated sensing transistor allows a passage of transistor current through the drain. When programmed, the antifuse dielectric, which is the gate of the integrated transistor, is subjected to a gate breakdown, shorting the gate to the channel and resulting in a decreased drain current. The integrated antifuse structure can also be wired in an array to provide a compact OTP memory array.

Abstract: A memory device 10 has an arrangement in which a memory thin film 4 is sandwiched between first and second electrodes 2 and 6, the memory thin film 6 contains at least rare earth elements, the memory thin film 4 or a layer 3 in contact with the memory thin film 4 contains any one of elements selected from Cu, Ag, Zn and the memory thin film 4 or the layer 3 in contact with the memory thin film 4 contains any one of elements selected from Te, S, Se. The memory device can record and read information with ease stably, and this memory device can be manufactured easily by a relatively simple manufacturing method.

Abstract: An object is to provide a semiconductor device mounted with memory which can be driven in the ranges of a current value and a voltage value which can be generated from a wireless signal. Another object is to provide write-once read-many memory to which data can be written anytime after manufacture of a semiconductor device. An antenna, antifuse-type ROM, and a driver circuit are formed over an insulating substrate. Of a pair of electrodes included in the antifuse-type ROM, the other of the pair of the electrodes is also formed through the same step and of the same material as a source electrode and a drain electrode of a transistor included in the driver circuit.

Abstract: Methods of fabricating a multi-layer semiconductor structure are provided. In one embodiment, a method includes depositing a first dielectric layer over a semiconductor structure, depositing a first metal layer over the first dielectric layer, patterning the first metal layer to form a plurality of first metal lines, and depositing a second dielectric layer over the first metal lines and the first dielectric layer. The method also includes removing a portion of the second dielectric layer over selected first metal lines to expose a respective top surface of each of the selected first metal lines. The method further includes reducing a thickness of the selected first metal lines to be less than a thickness of the unselected first metal lines. A multi-layer semiconductor structure is also provided.

Abstract: A tunable antifuse element (102, 202, 204, 504, 952) includes a substrate material (101) having an active area (106) formed in a surface, a gate electrode (104) having at least a portion positioned above the active area (106), and a dielectric layer (110) disposed between the gate electrode (104) and the active area (106). The dielectric layer (110) includes a tunable stepped structure (127). During operation, a voltage applied between the gate electrode (104) and the active area (106) creates a current path through the dielectric layer (110) and a rupture of the dielectric layer (110) in a rupture region (130). The dielectric layer (110) is tunable by varying the stepped layer thicknesses and the geometry of the layer.

Abstract: A method of forming an antifuse forms a material layer and then patterns the material layer into a fin. The center portion of the fin is converted into a substantially non-conductive region and the end portions of the fin into conductors. The process of converting the center portion of the fin into an insulator allows a process of heating the fin above a predetermined temperature to convert the insulator into a conductor. Thus, the fin-type structure that can be selectively converted from an insulator into a permanent conductor using a heating process.

Abstract: A metal-insulator diode is disclosed. In one aspect, the metal-insulator diode comprises a first electrode comprising a first metal, a first region comprising a first insulating material, a second region comprising a second insulating material, and a second electrode comprising a second metal. The first region and the second region reside between the first electrode and the second electrode. The second insulating material is doped with nitrogen. Note that the second insulating material may have an interface with either the first electrode or the second electrode.

Abstract: A metal-insulator diode is disclosed. In one aspect, the metal-insulator diode comprises first and second electrode and first and second insulators arraigned as follows. An insulating region has a trench formed therein. The trench has a bottom and side walls. The first electrode, which comprises a first metal, is on the side walls and over the bottom of the trench. A first insulator has a first interface with the first electrode. At least a portion of the first insulator is within the trench. A second insulator has a second interface with the first insulator. At least a portion of the second insulator is within the trench. The second electrode, which comprises a second metal, is in contact with the second insulator. The second electrode at least partially fills the trench.

Abstract: An integrated circuit comprises a plurality of layers including a first substrate with an on chip capacitor and a second substrate. In one embodiment, the second substrate has an on chip capacitor. The first and/or second substrate can include a sensor element, such as a magnetic sensor element.

Abstract: An antifuse device (120) that includes a bias element (124) and an programmable antifuse element (128) arranged in series with one another so as to form a voltage divider having an output node (F) located between the bias and antifuse elements. When the antifuse device is in its unprogrammed state, each of the bias element and antifuse element is non-conductive. When the antifuse device is in its programmed state, the bias element remains non-conductive, but the antifuse element is conductive. The difference in the resistance of the antifuse element between its unprogrammed state and programmed state causes the difference in voltages seen at the output node to be on the order of hundreds of mili-volts when a voltage of 1 V is applied across the antifuse device. This voltage difference is so high that it can be readily sensed using a simple sensing circuit (228).

Abstract: A method for verifying library components and designs on a via customizable ASIC, which may include the process of adding capacitors to model possible via sites of a model of an un-customized portion of or a whole ASIC, and replacing the capacitors with resistors to model where custom vias have been placed on the ASIC to implement a desired component or design. Views of this model may then be generated to verify the functionality of the component or design, and component models for timing, function and via customization may then be generated for the component library.

Abstract: In one aspect, a semiconductor device includes an array of memory cells. Individual memory cells of the array include a capacitor having first and second electrodes, a dielectric layer disposed between the first and second electrodes. Select individual capacitors are energized so as to blow the dielectric layer to establish a connection between the first and second electrodes such that, after blowing the dielectric layer, the second electrode is coupled to a cell plate generator establishing a bias connection therebetween. Cell plate bias connection methods are also described.

Abstract: A phase-change memory element for reducing heat loss is disclosed. The phase-change memory element comprises a composite layer, wherein the composite layer comprises a dielectric material and a low thermal conductivity material. A via hole is formed within the composite layer. A phase-change material occupies at least one portion of the via hole. The composite layer comprises alternating layers or a mixture of the dielectric material and the low thermal conductivity material.

Abstract: A method for making a one time programmable (OTP) memory array includes providing a wafer comprising a buried insulator layer and a semiconductor layer over the buried insulator layer and forming a plurality of bit lines in the semiconductor layer. Each of the plurality of bit lines comprise a portion of the semiconductor layer and the plurality of bit lines are separated from each other by isolation regions formed in the semiconductor layer. The method further includes forming an anti-fuse dielectric layer over and in physical contact with the plurality of bit lines and the isolation regions, and forming a plurality of word lines over and in physical contact with the anti-fuse dielectric layer.

Abstract: An electrical fuse and a first dielectric layer thereupon are formed on a semiconductor substrate. Self-assembling block copolymers containing two or more different polymeric block components are applied into a recessed region surrounded by a dielectric template layer. The self-assembling block copolymers are then annealed to form a pattern of multiple circles having a sublithographic diameter. The pattern of multiple circles is transferred into the first dielectric layer by a reactive ion etch, wherein the portion of the first dielectric layer above the fuselink has a honeycomb pattern comprising multiple circular cylindrical holes. A second dielectric layer is formed over the circular cylindrical holes by a non-conformal chemical vapor deposition and sublithographic cavities are formed on the fuselink. The sublithographic cavities provide enhanced thermal insulation relative to dielectric materials to the fuselink so that the electrical fuse may be programmed with less programming current.

Abstract: An antifuse having a link including a region of unsilicided semiconductor material may be programmed at reduced voltage and current and with reduced generation of heat by electromigration of metal or silicide from a cathode into the region of unsilicided semiconductor material to form an alloy having reduced bulk resistance. The cathode and anode are preferably shaped to control regions from which and to which material is electrically migrated. After programming, additional electromigration of material can return the antifuse to a high resistance state. The process by which the antifuse is fabricated is completely compatible with fabrication of field effect transistors and the antifuse may be advantageously formed on isolation structures.

Abstract: The disclosure relates generally to integrated circuit (IC) chip fabrication, and more particularly, to an e-fuse device including an opening, a first via and a second via in an interlayer dielectric, wherein the opening, the first via and the second via are connected to an interconnect below the interlayer dielectric; a dielectric layer that encloses the first via and the second via; and a metal layer over the dielectric layer, wherein the metal layer fills the opening with a metal, and wherein the first via and the second via are substantially empty to allow for electromigration of the interconnect during re-programming of the e-fuse device.

Abstract: There is provided a method of manufacturing a conductive layer of in a signal transmission substrate. The method includes sewing conductive thread in sheet-like material having an insulating property so as to form one of a plurality of low resistance regions using the conductive thread in a high resistance region formed by the sheet-like material, moving the conductive thread from an end point of a previously sewed low resistance region to a start point of a low resistance region to be sewed subsequently, repeating the sewing and moving steps to form the plurality of low resistance regions in the high resistance region, and forming a plurality of holes in the conductive layer by press working so that an electrical component attached to at least one of the plurality of holes is able to transmit a signal between neighboring ones of the plurality of low resistance regions.

Abstract: In an FPGA of a semiconductor device and a method of forming the FPGA, a first pattern having a voltage selectable conductivity is formed to connect first vias of the semiconductor device in parallel.

Abstract: An electrical antifuse comprising a field effect transistor includes a gate dielectric having two gate dielectric portions. Upon application of electric field across the gate dielectric, the magnitude of the electrical field is locally enhanced at the boundary between the thick and thin gate dielectric portions due to the geometry, thereby allowing programming of the electrical antifuse at a lower supply voltage between the two electrodes, i.e., the body and the gate electrode of the transistor, across the gate dielectric.

Abstract: A semiconductor device used as an ID chip is provided, of which operation is terminated when its role is finished or expires. According to the invention, an antenna circuit, a voltage detecting circuit, a current amplifier circuit, a signal processing circuit, and a fuse are provided over an insulating substrate. When large power is applied to the antenna circuit, a voltage is detected by voltage detecting circuit and a corresponding current is amplified by the current amplifier circuit, thereby the fuse is melted down. Also, when an anti-fuse is used, the anti-fuse can short an insulating film by applying an excessive voltage. In this manner, the semiconductor device has a function for making it invalid by stopping operation of the signal processing circuit when the role of the device is finished or expires.

Abstract: An antifuse circuit includes a terminal, an antifuse transistor, and a bias transistor. The antifuse transistor is formed on a substrate. The antifuse transistor is coupled to the terminal and includes a first gate terminal coupled to receive a first select signal. The bias transistor is coupled between the substrate and a bias voltage terminal. The bias transistor has a second gate terminal and is operable to couple the bias voltage terminal to the substrate responsive to an assertion of a bias enable signal at the second gate terminal.

Abstract: The present invention provides a method of integrating a structure, e.g. a fuse, for use in a semiconductor device, the method comprises several steps, the first step is providing a first layer of sacrificial material (1) on a substrate. The second step is providing the structure (5) on the first layer of sacrificial material, the structure having two terminal portions. The third step is providing a second layer of sacrificial material (3) over the first layer of sacrificial material and over a length of the structure between the terminal portions such that the length of the structure is surrounded by sacrificial material, said length defining a usable portion of the structure. The fourth step is providing a layer of dielectric material such that the first and second layers of sacrificial material and the structure are encased by the layer of dielectric material and the substrate. The fifth step is forming a passage through the dielectric material to provide access to the sacrificial material.

Abstract: A semiconductor device having a variable capacitance capacitor and a method of manufacturing the same are disclosed. An example semiconductor device includes a capacitor having a bottom electrode, a dielectric layer and an upper electrode, formed on a semiconductor substrate. The example semiconductor also includes a first insulating layer formed on the semiconductor substrate to cover the capacitor, a plurality of first contact plugs formed in a plurality of first via holes of the first insulating layer, each of which is electrically connected to either the bottom electrode or the upper electrode, a first metal wiring formed on the first insulating layer and connected to the bottom electrode through the first contact plug, a second contact plug formed on the first insulating layer and connected to the upper electrode through the first contact plug, and a second insulating layer formed on the first insulating layer to cover the first metal wiring and the second contact plug.

Abstract: A semiconductor device includes an anti-fuse portion and a memory cell portion each including a MOSFET structure having a gate insulating film formed on a semiconductor substrate and a gate electrode formed on the gate insulating film; wherein a depletion ratio in the gate electrode of the anti-fuse portion is different from the depletion ratio in the gate electrode of the memory cell portion, and the depletion ratio in the gate electrode of the anti-fuse portion is lower than the depletion ratio in the gate electrode of the memory cell portion.

Abstract: An anti-fuse one-time-programmable (OTP) nonvolatile memory cell has a P well substrate with two P? doped regions. Another N+ doped region, functioning as a bit line, is positioned adjacent and between the two P? doped regions on the substrate. An anti-fuse is defined over the N+ doped region. Two insulator regions are deposited over the two P? doped regions. An impurity doped polysilicon layer is defined over the two insulator regions and the anti-fuse. A polycide layer is defined over the impurity doped polysilicon layer. The polycide layer and the polysilicon layer function as a word line. A programmed region, i.e., a link, functioning as a diode, is formed on the anti-fuse after the anti-fuse OTP nonvolatile memory cell is programmed. The array structure of anti-fuse OTP nonvolatile memory cells and methods for programming, reading, and fabricating such a cell are also disclosed.

Abstract: An anti-fuse structure and a method of fabricating the same are described. The anti-fuse structure is disposed over a substrate having at least one device and a copper layer therein. The anti-fuse structure includes a bottom conductive layer, an insulating layer and a top conductive layer. The bottom conductive layer is disposed over and electrically connected with the copper layer. The insulating layer is conformally disposed over the bottom conductive layer covering a corner or a downward turning portion of the bottom conductive layer to form a turning portion of the insulating layer. The top conductive layer is conformally disposed over the insulting layer covering the turning portion of the insulating layer.

Abstract: The invention includes semiconductor assemblies having two or more dies. An exemplary assembly has circuitry associated with a first die front side electrically connected to circuitry associated with a second die front side. The front side of the second die is adjacent a back side of the first die, and a through wafer interconnect extends through the first die. The through wafer interconnect includes a conductive liner within a via extending through the first die. The conductive liner narrows the via, and the narrowed via is filled with insulative material. The invention also includes methods of forming semiconductor assemblies having two or more dies; and includes electronic systems containing assemblies with two or more dies.

Abstract: A semiconductor memory structure based on gate oxide break down is constructed in a deep N-well. Thus, the electrical field over the programmable element during the transient procedure of gate oxide break down can be controlled to achieve the best memory programming results. The conductivity of the programmed memory cell is increased greatly and conductivity variation between the memory cells is reduced. This is achieved by adding a body bias during the programming process. The body here refers to a P-well formed within the deep N-Well. Furthermore, the read voltage offset is reduced greatly with this new memory configuration. These improved programming results will allow faster read speed and lower read voltage. This new structure also reduces current leakage from a memory array during programming.

Abstract: A memory device including at least one first memory element comprising a first layer of amorphous carbon over at least one second memory element comprising a second layer of amorphous carbon. The device also includes at least one first conductive layer common to the at least one first and the at least one second memory elements.

Abstract: Solid-state memories are disclosed that are comprised of cross-point memory arrays. The cross-point memory arrays include a first plurality of electrically conductive lines and a second plurality of electrically conductive lines that cross over the first plurality of electrically conductive lines. The memory arrays also include a plurality of memory cells located between the first and second conductive lines. The memory cells are formed from a metallic material, such as FeRh, having the characteristic of a first order phase transition due to a change in temperature. The first order phase transition causes a corresponding change in resistivity of the metallic material.

Abstract: A non-volatile memory device and methods of fabricating the device according to example embodiments involve a stacked layer structure. The non-volatile memory device may include at least one first horizontal electrode including a first sidewall and a second sidewall; at least one second horizontal electrode including a third sidewall and a fourth sidewall; wherein the third sidewall may be disposed to face the first sidewall; at least one vertical electrode may be interposed between the first sidewall and the third sidewall, in such a way as to cross or intersect each of the at least one first and second horizontal electrodes, and; at least one data storage layer that may be capable of locally storing a change of electrical resistance may be interposed where the at least one first horizontal electrode and the at least one vertical electrode cross or intersect and where the at least one horizontal electrode and the at least one vertical electrodes cross or intersect.

Abstract: A semiconductor device includes a semiconductor substrate, and an electrical fuse provided on the semiconductor substrates. The electrical fuse includes a first fuse link and a second fuse link mutually connected in series, a first current inlet/outlet terminal (first terminal) and a second current inlet/outlet terminal (second terminal) respectively provided at an end and the other end of the first fuse link, and a third current inlet/outlet terminal (second terminal) and a fourth current inlet/outlet terminal (third terminal) provided at an end and the other end of the second fuse link.

Abstract: An integral circuit protection device includes a substrate disposed between first and second terminals. The substrate is composed of a resistive material. A first conductive layer is disposed on a first surface of the substrate and in electrical contact with the first terminal. A second conductive layer is disposed on a second surface of the substrate. A first electrically insulating layer is disposed on the second conductive layer and substantially covers the second conductive layer. The first electrically insulating layer includes an aperture. A fuse element is disposed on the first electrically insulating layer and is in electrical contact with the second conductive layer through the aperture and in electrical contact with the second terminal. The fuse element is in electrical series with the resistive material. A second electrically insulating layer is disposed over the fuse element.

Abstract: A semiconductor device (200) includes: an electrical fuse (100) including: a lower layer interconnect (120) formed on a substrate; a via (130) provided on the lower layer interconnect (120) so as to be connected to the lower layer interconnect (120); and an upper layer interconnect (110) provided on the via (130) so as to be connected to the via (130), the electrical fuse being cut, in a state after being cut, through formation of a flowing-out portion, the flowing-out portion being formed when an electrical conductor forming the upper layer interconnect (110) flows outside the upper layer interconnect (110); and a guard upper layer interconnect (152) (conductive heat-absorbing member) formed in at least the same layer as the upper layer interconnect (110), for absorbing heat generated in the upper layer interconnect (110).

Abstract: Provided are an antifuse and methods of operating and manufacturing the same. The antifuse may include first and second conductors separate from each other; a dielectric layer for an antifuse between the first and second conductors; and a diffusion layer between one of the first and second conductors and the dielectric layer.

Abstract: An input protection circuit comprises a semiconductor chip, an internal circuit disposed on the semiconductor chip, a first input/output terminal which is disposed on the semiconductor chip and connected to the internal circuit, a second input/output terminal which is disposed on the semiconductor chip, connected to the internal circuit and disposed at a position adjacent to the first input/output terminal, and a fusing part which is disposed on the semiconductor chip and connected between the first and second input/output terminals.

Abstract: A nonvolatile memory device including a lower electrode, a resistor structure disposed on the lower electrode, a diode structure disposed on the resistor structure, and an upper electrode disposed on the diode structure. A nonvolatile memory device wherein the resistor structure includes one resistor and the diode structure includes one diode. An array of nonvolatile memory devices as described above.

Abstract: Provided may be a multi-level anti-fuse and methods of fabricating and operating the same. The multi-level anti-fuse may include at least three anti-fuses having a plurality of anti-fuses connected in parallel constituting a parallel connection structure and at least one anti-fuse connected to the parallel connection structure in series, wherein the parallel connection structure may have a smaller resistance than the resistance of the anti-fuse connected in series, the plurality of anti-fuses connected in parallel may include dielectric layers having different thicknesses from one another, and the breakdown voltages of each dielectric layer may be different from one another.

Abstract: In one embodiment a fuse region includes an insulating layer disposed on a substrate, a fuse disposed on the insulating layer and including a fuse barrier pattern and a fuse conductive pattern, which are stacked, and a supporting plug disposed beneath the fuse, and penetrating the insulating layer and the fuse barrier pattern.

Abstract: A structure configured to disconnect circuit elements. The structure generally includes a dielectric layer over a light-absorbing structure, and a lens over the dielectric layer and the light-absorbing structure, configured to at least partially focus light onto the light-absorbing structure. The light-absorbing structure absorbs a first wavelength of light with a minimum threshold efficiency, the lens is substantially opaque to the first wavelength of light, and the dielectric layer is substantially transparent to the first wavelength of light. The structure advantageously provides improved reliability and smaller chip area, thereby increasing the yield of the manufacturing process and the numbers of die per wafer (both gross and good).

Abstract: A semiconductor device with a capacitor and a fuse, and a method for manufacturing the same are described. The semiconductor device comprises a semiconductor substrate having a capacitor region and a fuse region defined therein, a insulating layer over the semiconductor substrate, a storage node hole formed in the insulating layer, a barrier metal in the storage node hole, a dielectric layer formed on the barrier metal and the insulating layer, a lower metal layer for a plate electrode filling the storage node hole such that it is flush with the dielectric layer, an upper metal layer for the plate electrode on the dielectric layer and lower metal layer for the plate electrode; and a fuse metal layer formed of the same material as that of the upper metal layer for the plate electrode on the dielectric layer in the fuse region.

Abstract: A semiconductor device includes a semiconductor substrate, and an electrical fuse provided on the semiconductor substrate. The electrical fuse includes a first fuse link and a second fuse link mutually connected in series, a first current inlet/outlet terminal (first terminal) and a second current inlet/outlet terminal (second terminal) respectively provided at an end and the other end of the first fuse link, and a third current inlet/outlet terminal (second terminal) and a fourth current inlet/outlet terminal (third terminal) provided at an end and the other end of the second fuse link.

Abstract: Disclosed are embodiments of a circuit and method for electroplating a feature (e.g., a BEOL anti-fuse device) onto a wafer. The embodiments eliminate the use of a seed layer and, thereby, minimize subsequent processing steps (e.g., etching or chemical mechanical polishing (CMP)). Specifically, the embodiments allow for selective electroplating metal or alloy materials onto an exposed portion of a metal layer in a trench on the front side of a substrate. This is accomplished by providing a unique wafer structure that allows a current path to be established from a power supply through a back side contact and in-substrate electrical connector to the metal layer. During electrodeposition, current flow through the current path can be selectively controlled. Additionally, if the electroplated feature is an anti-fuse device, current flow through this current path can also be selectively controlled in order to program the anti-fuse device.

Abstract: An anti-fuse includes a gate dielectric layer formed over a substrate, a gate electrode including a body portion and a plurality of protruding portions extending from the body portion, wherein the body portion and the protruding portions are formed to contact on the gate dielectric layer, and a junction region formed in a portion of the substrate exposed by sidewalls of the protruding portions.