Semiconductor device

Abstract: A semiconductor device having a semiconductor layer, in which an active device such as a MOS or bipolar transistor in the front surface area of the semiconductor layer, and a device for communicating the front and rear surfaces of the semiconductor layer is formed therein in connection with one of the electrodes of the active device and exposes to a groove formed in the rear surface of the semiconductor layer. A three-dimensional semiconductor device including at least two semiconductor devices stacked one on another is also disclosed.

Description: The invention refers to a semiconductor device. US-A-4,505,799 discloses a semiconductor device comprising a semiconductor layer which has several grooves formed in a rear surface portion of the semiconductor layer. In the front surface area of the semiconductor layer, active devices are formed which are coated in the front side of the substrate with a number of oxides and an ion-sensitive membrane. Each active device is disposed to one groove. For the electrical contact of the active devices, the groove is coated with a metallic contact. US-A-4,601,096 discloses a semiconductor device, in particular a field effect transistor for operation at microwave and millimeter frequencies. The substrate is a semiconductor layer and the gate device is a Schottky-type junction. In the rear surface of the semiconductor substrate a groove is formed and an active device, the transistor source, is exposed to the groove. A metal film is formed on the backside of the semiconductor layer and contacts the source region directly. By the contact metal, the transistor performance at microwave and millimeter frequencies is improved. Moreover, a semiconductor substrate including conventional semiconductor devices or an integrated circuit (IC) is known, which is provided with one terminal for e.g. a drain of one of the devices on the rear surface and with other terminals for the devices on the front main surface in the form of metallic contact terminals or electrodes at an insulating oxide film. For instance, IEEE Power Electronics Specialists Conference Record, 1985, pp229-233, discloses a cross section of a power MOSFET having a protector function therein. In this case, various elements or devices are formed in the front main surface of the semiconductor substrate, and almost all of their electrode terminals are formed on the front main surface, while only one output drain terminal is formed on the rear surface. In such a conventional case, the rear surface of the semiconductor substrate is contacted with a mounting substrate, and it is enough to provide only one voltage source to the semiconductor substrate. Further, even when the front main surface including the semiconductor IC is bonded to the mounting substrate facing thereto, it is unnecessary to provide a plurality of electrodes independently for applying different voltages on the rear surface of the semiconductor substrate having a certain thickness. Hence, it is not considered to supply a plurality of different voltages or currents from the rear surface to the front main surface of the semiconductor substrate therethrough while being isolated from one another. In a conventional three-dimensional laminated semiconductor substrate structure, as disclosed in Nikkei Micro Device, 1985, July, pp175-192, the signal communication between the front and rear surfaces of the semiconductor substrate on which various devices or ICs are formed on the front surface, is developed insufficiently. Accordingly, when two laminated semiconductor substrates are further laminated one on another, the desired electrode portions of the two substrates are positioned and are securely connected in order to carry out the signal communication between the two substrates. However, in this case, it is rather difficult to provide wirings for connecting the front and rear surfaces of the substrates. Another conventional three-dimensional laminated semiconductor substrate structure is prepared by stacking a plurality of semiconductor substrates, as disclosed in IEEE Computer, 1984, January, p69, by Jan. Grinberg. In this embodiment, an ohmic wiring penetrating the substrate is produced by forming a p⁺-type region passing through an n-type semiconductor substrate using a p-type aluminum dopant diffusion based on the heat transfer diffusion by the aluminum dot. The interconnection between the two substrates is realized by contacting cross-linked two metallic microbridges for connection. In this case, however, since the feed through portion is composed of the p⁺-type portion of the P⁺N junction and a separation of P⁺N junction is used, it is difficult to control a distribution capacity due to the PN junction and upper and lower resistance values of the p⁺-type portion. Further, since the microbridges are not securely connected to each other, it is insufficient in stability of the mechanical structure for linking the two substrates, and its sufficient or ideal isolation from the other portions can not be performed. It is the object of the invention to provide a semiconductor device by which a signal communication or an ohmic connection between the front and the rear surface of the semiconductor substrate can be performed and by which a perfect isolation of the communicating members from other portions of the substrate is provided. This object is solved by a semiconductor device having the features of claim 1. Preferred embodiments are disclosed in the dependent claims. In the following, the description will be described in more details by the Figures. Fig. 1 is a cross sectional view of a first embodiment of the first semiconductor layer in a semiconductor device including a MOS transistor according to the present invention; Fig.2 is a cross sectional view of a second embodiment of the first semiconductor layer in a semiconductor device including a vertical MOS transistor according to the present invention; Fig. 3 shows the arrangement of a plurality of terminals in a groove; Fig. 4 is a cross sectional view of a complete embodiment of a two-layer lamination three-dimensional semiconductor device according to the present invention, including the semiconductor layer shown in Fig. 1; Fig. 5 is a cross sectional view of a further embodiment of the first semiconductor layer in a semiconductor device including a MOS transistor according to the present invention; Fig. 6 is a cross sectional view of another complete embodiment of a two-layer lamination three-dimensional semiconductor device according to the present invention. Fig. 7 is a bottom view of the first semiconductor layer, showing 2x8 terminals for 2x8 bits of active devices formed in each of four grooves on the rear surface of a semiconductor substrate; Fig. 8 is a schematic side view of a further embodiment according to the present invention, including four-layer lamination three-dimensional semiconductor device composed of four semiconductor layers; and Fig. 9 is a cross sectional view of a further embodiment of the first of a semiconductor layer in a semiconductor device including a bipolar transistor according to the present invention. Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the views, there is shown in Fig. 1 the first embodiment of the first semiconductor layer in a semiconductor device such as a MOS device of a silicon-on-insulator (SOI) structure according to the present invention. In Fig. 1, a silicon oxide (SiO₂) film 2 is formed on the upper or front surface of a silicon (Si) semiconductor substrate 1, and a bottom groove 13 is formed on the lower or rear surface of the substrate 1 to reach the silicon oxide film 2 in a conventional manner, e.g., some etching processes similar to those employed in a silicon pressure sensor production. A p-type semiconductor crystalline layer 3 is formed on the silicon oxide film 2 using a conventional SOI technique. An n⁺-type source 4 is formed in the surface area of the silicon crystalline layer 3, and a n⁺-type drain 5 is formed in the active silicon layer of the SOI type to penetrate deeply the silicon crystalline layer 3 and the silicon oxide film 2 and to reach the bottom (seen from the rear surface, i.e., the upper end in Fig. 1) of the groove 13 on the rear surface of the substrate 1. An insulating gate film 6 is formed on the front surface of the silicon crystalline layer 3 to bridge between the source 4 and the drain 5, and a field oxide film 7 is also formed on the surface of the layer 3. A source electrode 8, a drain electrode 9 and a gate electrode 10 are attached to the surfaces of the source 4, the drain 5 and the gate film 6, respectively, in a conventional manner. An insulating oxide film 11 is also formed on the rear surface of the substrate 1 in a conventional manner to cover the rear surface thereof. In this embodiment, when the thickness of the silicon substrate 1 is designed to approximately 300µ to 500µ, its thickness of the remaining upper portion (not shown) which defines the bottom of the groove 13 may be designed to approximately 10µ to 30µ. A particular patterning method is required in order to form a rear contact portion 12A and a rear surface wiring portion 12B integrally connected thereto. That is, since the contact portion 12A and the rear surface wiring portion 12B are apart from each other with a somewhat long distance with respect to the rear end surface, a usual photo-lithography process can not be applied for the patterning. The patterning can be carried out in a lithography step by exposing with the light beam of an ultraviolet to far ultraviolet ray range using a mask to be placed in close proximity to the substrate 1 and an optical system including a laser light source with a well parallelism. A direct pattern etching, now being developed, where a photo-chemical reaction is directly conducted in a excited etching gas atmosphere using a pattern mask and a laser beam, may be also applicable. As described above, in the first embodiment shown in Fig. 1, the n⁺-type region 5 penetrates the epitaxial layer 3 to the bottom groove 13 of the rear surface of the substrate 1 and is connected to the wiring portion 12B formed on the rear surface of the substrate 1 through the contact portion 12A, and the wiring portion 12B is isolated from the substrate 1 by the insulating oxide film 11 covering the side and rear surfaces of the substrate 1 and the silicon oxide film 2 covering the front surface of the substrate 1. Therefore, the n⁺-type drain 5 can be provided with one connection terminal as the drain terminal 9 on the front surface of the substrate 1 and another independent connection terminal as the rear wiring portion 12B on the rear surface of the substrate 1 separate from the other portions. The rear terminals 12A and 12B are connected to a voltage source separate from the voltage of the substrate bulk. In the embodiment of Fig. 1, although only the drain 5 is connected to the two terminals on the front and rear surfaces of the substrate 1, other active regions such as the source 4 of the MOS transistor may be, of course, connected to the two terminals on the front and rear surfaces of the substrate 1. That is, one of the electrodes of the active device such as the MOS transitor can be communicated to the front and rear surfaces or the substrate. Further, an anode or cathode of a diode formed in the surface area of the substrate may be contacted to the two terminals on the front and rear surfaces of the substrate. In the SOI device shown in Fig. 1, an ohmic connection with the n⁺-type drain 5 of the MOS transistor can be performed using the contact portion 12A on the rear surface of the substrate 1. Thus, when the signal processing is conducted by the N-channel EDMOS formed in the silicon crystalline layer 3 formed on the silicon oxide film 2, the signal can be transmitted from the drain 5 to another member such as an inverter positioned in the same plane as the drain 5 through the drain electrode 9 and to other members on the front surface of another substrate positioned under the substrate 1 including the drain 5 via the contact portion 12A and the rear wiring portion 12B in a multi-layer lamination three-dimensional semiconductor device composed of at least two semiconductor substrates stacked one on another. In the first embodiment described above, it is readily understood that the following effects and advantages can be obtained. Since the electrode such as the drain is connected to the two terminals on the front and rear surfaces of the substrate, a separation of an output current is advantageously performed in a power device where a large current flows in the direction perpendicular to the substrate, and a plurality of terminals for one drain can be advantageously provided on the front and rear surfaces in the MOS transistor. Since in addition to the front surface including various devices or ICs, a plurality of wiring terminals for electrodes can be separately provided along side surfaces of a groove formed on the rear surface of the substrate, a communication of a plurality of signals between the front and rear surfaces of the substrate can be simultaneously carried out. Further, this parallel signal communication can be performed by the ohmic contact and can be controlled by control signals of an active device having three electrode terminals such as a MOS transistor, and thus a switching function and an amplifying action can be also possible in the same time. When a plurality of semiconductor substrates including various devices and ICs on their front surfaces are laminated one on another and the desired electrode portions arc aligned and are securely connected by heat melting to form a multi-layer lamination three-dimensional semiconductor device structure, a plurality of signals can be communicated in parallel among the front and rear surfaces from the top to bottom substrates. Thus, a parallel processing, a high functioning and a large capacity of an information processor such as a microcomputer and an image processor may be performed. Further, the stacked semiconductor device of the present invention can be applied to realize a laminated three-dimensional parallel processing intelligent sensor including a first layer having a plurality of sensor devices, and second and third layers having operational devices or memories. By using a laminated three-dimensional semiconductor device prepared by stacking a plurality of semiconductor layers, the defects and disadvantages arise in a conventional IC highly integrated in a flat plane can be removed or largely improved. That is, a chip size can be minimized, and a wiring length within the chip can be largely reduced to improve the transmission speed of the signal through the chip. Further, a layout limitation of cells and wiring can be reduced, and an inferior rate of manufactured chips can be considerably reduced. In Fig. 2, there is shown a second embodiment of the first semiconductor layer in a semiconductor device including a vertical MOS transistor according to the present invention, having basically thee same construction as that of the first embodiment shown in Fig. 1. In Fig. 2, an n-type epitaxial layer 15 is grown on a p⁻-type semiconductor substrate 14, and an n⁺-type buried drain layer 16 is formed in the substrate 14 between the lower end portion of the epitaxial layer 14 and a groove 13 formed in the rear surface of the substrate 14 to penetrate the substrate 14 and to reach the bottom (the upper end in Fig. 2) of the groove 13. The substrate 14 functions for electrically separating the n⁺-type buried drain layer 16. A field oxide film 7 covers the surface of the epitaxial layer 14 in the same manner as the first embodiment. A pair of p-type base regions 17A and 17B are formed in the surface portion of the epitaxial layer 15 at a certain distance away from each other, and a pair of n⁺-type source regions 18A and 18B are formed in the surface portions of the respective base regions 17A and 17B. An insulating gate film 19 is formed on the surface of the epitaxial layer 15 between the parts of the two source regions 18A and 18B formed in the drain regions 17A and 17B, and a highly impurity-doped silicon polycrystalline gate electrode 20 is formed in the insulating gate film 19. A pair of source-base common electrodes 21A and 21B are attached to the surfaces of the parts of the sources 18A and 18B and drains 17A and 17B. These parts described above can be formed in a conventional manner. In this embodiment, the buried layer 16 of the vertical MOS transistor formed in the front main surface area exposes to the bottom of the groove 13, and the bottom of the buried layer 16 is contacted with a rear contact portion 12A which is integrally connected to a rear surface wiring portion 12B in the same manner as the first embodiment. A pair of p-type separation regions 22 may be formed in the epitaxial layer 15 in order to improve the separation of the drains from the other members. In the second embodiment shown in Fig. 2, since the drain portions can be partially restricted, the drain electrode terminals can be separately provided on the rear surface of the substrate. Hence, a plurality of vertical MOS transistors having each drain electrode terminal on the rear surface can be produced in the same substrate. When the chip is so mounted that the wiring may be carried out from both front and rear surfaces of a substrate, a plurality of vertical MOS transistors can be arranged in the same substrate. Further, of course, the same effects and advantages as those of the first embodiment of the present invention can be obtained in the second embodiment. In Fig. 3, there is shown the arrangement of a plurality of terminals in a groove of a semiconductor device according to the present invention, which is an upside-down view as compared with Figs. 1 and 2, having the same structure as that of the first or second embodiment shown in Fig. 1 or 2, except that a plurality of rear output terminals are formed in one groove of the rear surface of a substrate, as hereinafter described, and thus the other members may be omitted from Fig. 3 and the following description for the brevity. In this embodiment, a semiconductor substrate 23 is formed with a groove 13 in the rear surface (upper surface in Fig. 3) to form a non-etched thick portion 23A and an etched thin portion 23B, as shown in Fig. 3A, and then is formed with an insulating oxide film 24 over the groove 13 and the rear surface in the same manner as the previous embodiments shown in Figs. 1 and 2. Then, a plurality of output terminals (only two terminals are shown in Fig. 3) 25 and 26, which correspond to a combination of the contact portion 12A and the rear surface wiring portion 12B shown in Figs. 1 and 2, are formed in the groove 13 in the same manner as the previous embodiments, as shown in Figs. 3B and 3C. In this case, the plurality of rear electrode terminals such as drain output terminals are formed at the predetermined interval, as shown in Fig. 3C. For instance, a drain of a MOS transistor is reverse-biased in a PN junction state, and therefore is separated by itself from the others. Further, in case of an active device which is not separated by itself, it is necessary to separate each electrode portion formed in an etched thin portion 23b by forming a separation area using a PN junction separation or an insulating groove separation, thereby separately picking up each electrode output. Further, another electrode terminal may be separately formed on the rear surface by supplementarily forming another groove in the same manner as described above. There is shown in Fig. 4 a complete embodiment of a two-layer lamination three-dimensional semiconductor device according to the present invention. In this embodiment, a first semiconductor layer 101 having, for instance, the same structure as the first or second embodiment shown in Fig. 1 or 2, and a second semiconductor layer 102 of a conventional IC having a CMOS structure are laminated one on another at their certain electrodes by a heat-pressure connection method. In Fig. 4, the upper first layer 101 has the same construction as the first embodiment shown in Fig. 1, and the detailed description thereof can be omitted. Then, the second semiconductor layer 102 will be described as follows. A field oxide film 7a is formed over the front or upper surface of an n-type semiconductor substrate 27, and in the upper surface area of the substrate 27, a p-type well region 28 is formed. A pair of p⁺-type well contact regions 29 are formed in the contact areas between the substrate 27 and the well region 28, and an n⁺-type base contact region 30, a p⁺-type source region 31 contacted therewith, a p⁺-type drain region 32, an n⁺-type drain region 33 and an n⁺-type source region 34 are formed in the surface portions of the substrate 27 and the well region 28 (the former three in the substrate 27 and the latter two in the well region 28). A V DD electrode 40, a V SS electrode 41 and a CMOS output electrode 42 are formed on the contact and source regions 30 and 31, the two drain regions 32 and 33, and the well contact and source regions 29 and 34, respectively. An insulating film 39 is formed over the upper surface of the substrate 27, and two highly concentrated silicon gates 35 and 36 and two gate oxide films 37 and 38 thereunder are formed in the insulating film 39. A CMOS gate contact electrode 43A and another electrode 43B are formed in the insulating film 39. Two polyimide film layers 44 and 45 and upper and lower two-layer gold-titanium (Au/Ti) alloy layer electrodes 46U, 46L, 47U and 47L are formed, as hereinafter described. As shown in Fig. 4 the coupling of the upper and lower semiconductor layers 101 and 102 is performed in almost the same way as that disclosed in the report. "Promising New Fabrication Process Developed For Stacked LSI's" of International Electron Devices Meeting Technical Digest, 1984, pp816, by M. Yasumoto et al. In this method, first, two two-layer gold-titanium (Au/Ti) alloy layers 46L and 47L are formed on the two aluminum electrodes 43A and 43B, and then a polyimide layer 45 is coated over the surface of the substrate up to the same height as that of the Au/Ti layer electrodes 46L and 47L. Then, the coated surface of the substrate is treated by a plasma oxygen (O₂) etching to expose the Au/Ti electrodes 46L and 47L and to make flat the surface of the polyimide layer 45 and the Au/Ti electrodes 46L and 47L in the same time. On the other hand, at the rear surface of the first layer 101, the aluminum electrode 12B integrally connected to the contact portion 12A and another aluminum electrode 12C are prepared, in advance, in the proper positions, and then two Au/Ti layer electrodes 46U and 47U are formed on the two aluminum electrodes 12B and 12C so as to coincide with the Au/Ti electrodes 46L and 47L of the second layer 102 when the two layer 101 and 102 are positioned to align to the desired position. Meanwhile an insulating film 11B is applied on the insulating oxide film 11 of the rear surface of the substrate 1. Then, a polyimide layer 44 is coated over the rear surface of the substrate and the coated rear surface is also treated to a flat surface in the same manner as the flattened front surface of the second layer 102, as described above. The two flattened surfaces of the two layers 101 and 102 are contacted with each other so as to contact the Au/Ti electrodes 46U and 47U of the first layer 101 with the Au/Ti electrodes 46L and 47L of the second layer 102 in the right position, and then the pairs of Au/Ti electrodes 46U, 46L and 47U, 47L are securely connected to each other by the heat-pressure melting method, thereby coupling the first and second semiconductor layers 101 and 102. When the two layers 101 and 102 are connected with a sufficient strength by connecting only the electrode portions, dummy electrodes may be further additionally formed on the contact surfaces of the two devices. Further, although one example for securely connecting the Au/Ti electrodes is described hereinbefore, however, the present invention is not restricted to this example, and, of course, other proper methods may be used. In this embodiment, the polyimide layers 44 and 45 effectively function for damping the stresses and giving the electric insulation. Further, the etched groove 13 may be closed by filling with the polyimide material in a devised manufacturing process. In this case, as shown in Fig. 4, by the output signal from the drain contact electrodes 12A and 12B of the upper first layer 101, the switching may be carried out by driving the gate 43A of the CMOS inverter in the lower second layer 102. Further, in the embodiment, of course, the same results, effects and advantages as those of the previous embodiments of the present invention can be obtained. In Fig. 5, there is shown a further embodiment of the first semiconductor layer in a semiconductor device according to the present invention, having basically the same structure as the first embodiment shown in Fig. 1. In this embodiment, a field oxide film 7 is formed on the front main surface of an n-type semiconductor substrate 51 having a groove 13 in the rear surface, and an insulating oxide film 11 is formed over the groove 13 and the rear surface of the substrate 51. In an etched thin portion 54 of the substrate 51, a low resistance ohmic region 56 is formed to penetrate the thin portion 54 from the front surface to the bottom (the upper surface of the groove 13 in Fig. 5) of the groove 13, and the ohmic region 56 is surrounded by insulating films 55 for electrically isolating or separating the ohmic region 56 from the substrate 51. The insulating films 55 are formed by a fine ditching step and an oxidizing step, and the ohmic region 56 can be formed by, for example, silicon polycrystalline or by doping an impurity in a high concentration into silicon monocrystalline. The ohmic region 56 may be also formed by using a metallic material having a high melting point such as molybdenum (Mo) or tantalum (Ta) in a contrived producing process. A combination of a rear surface contact member 12A and a rear surface electrode is contacted to the bottom of the ohmic region 56 in the groove portion 13 in the same manner as described above. In the front surface area of the substrate 51, a N-channel MOS transistor is provided. That is, an n⁺-type source 58 and an n⁺-type drain 59 are formed at a proper distance, and a silicon gate 61 and a gate oxide film 60 therebelow are formed in a conventional manner. The upper end surface of the ohmic region 56 and the silicon gate 61 are electrically coupled through respective electrodes 62A and 62B formed thereon. In this embodiment, as described above, the front and rear surfaces of the substrate 51 are communicated via the low resistance ohmic region 56 while the ohmic region 56 is insulated from the surroundings. Accordingly, the silicon gate 61 in the front surface is connected to the rear surface electrodes 12A and 12B through the front surface electrodes 62A and 62B and the ohmic region 56. Hence, the N-channel MOS transistor in the front main surface can be driven by applying a voltage to the rear surface electrodes 12A and 12B. The same effects and advantages as those in the previous embodiments of the present invention can be obtained. Although the silicon gate in the front surface is coupled to the rear surface electrode in this further embodiment, another part such as the drain or the source in the front surface can be, of course, connected to the rear surface electrode. Further, a plurality of the low resistance ohmic regions 56 which connects the N-channel MOS transistor formed in the front surface and the rear surface electrodes 12A and 12B, can be provided in one groove 13 in the same manner as shown in Fig, 3, and thus the detailed description thereof can be omitted. In Fig. 6, there is shown another complete embodiment of a two-layer lamination three-dimensional semiconductor device according to the present invention. In this embodiment, an upper first semiconductor layer 103 and the lower second semiconductor layer 102 shown in Fig. 4 are coupled in the same manner as the one shown in Fig. 4. The first semiconductor layer 103 is prepared by further including substantially the same low resistance ohmic region 56 and MOS transistor shown in Fig. 5 using the SOI substrate in the right half side portion of the first semiconductor layer 101 shown in Fig. 4. Consequently, the detailed description of the first and second semiconductor layers 103 and 102 can be omitted for the brevity of the description. In this case, of course, the same effects, advantages and results as those of the previous complete embodiment of the present invention can be obtained as well. Fig. 7 is a bottom view of the first semiconductor layer. Fig. 7 shows four grooves A, B, C and D formed on the rear surface of the first semiconductor layer such as the one of the present embodiments shown in Figs. 1, 2 and 5, and 2x8=16 rear contact terminals 65 formed in each of the grooves A, B, C and D for 2x8=16 bits of the wiring. In this embodiment, in fact, a plurality of semiconductor layers are stacked one on another to constitute a multi-layer lamination three-dimensional semiconductor device, and 16 bits of signals can be processed in parallel between the front and rear surfaces of each device and from the uppermost device to the lowermost device and vice versa. In this case, for example, all contact terminals 65 of one groove A may be connected to lower resistance ohmic regions therein, and all contact terminals 65 of another groove B may be contacted with one electrodes such as drain terminals of active devices such as MOS transistors. When the signals are transmitted from the lower device to the upper device and vice versa in the same time, for instance, the terminals of the grooves C and D may be separately used for the signal transimissions in the upper and lower directions, respectively. In Fig. 8, there is shown a further embodiment of four semiconductor layers 105, 106, 107 and 108 which constitute a four-layer lamination three-dimensional semiconductor device according to the present invention. In this embodiment, the four layers are so stacked that the grooves 13 of the two adjacent layers 105 and 106, 106 and 107 or 107 and 108 may not be aligned along vertical straight lines. When the four layers are stacked one on another, as shown in Fig. 8 and each device includes four grooves, as shown in Fig. 7, 32 bits of signals of the two grooves and 32 bits of signals of the other two grooves may be processed in parallel in the upper and lower directions in the same time, thereby effectively utilizing the three-dimensional lamination semiconductor device. Further, according to the present invention, a plurality of semiconductor layers of the present invention are stacked one on another, in which, for instance, the layers are designed to have respective particular functions, such as one device including sensor, some other layers including operational ICs, still some other layers including memories, another layer including a comparator IC and so forth, and they may be uses as a self-library. Each layer may be designed independently for a particular purpose. According to the present invention, a silicon-on-glass substrate and a silicon-on-sapphire substrate may be also conveniently used to produce a semiconductor layer. The glass substrate and the sapphire substrate can be formed with a groove or a hole to a silicon layer in the rear surface by an etching or a reactive ion etching (RIE). As to the inclination of the groove 13, e.g., shown in Fig. 8, it may be determined by a crystalline surface such as a (111) surface, but the inclined angle may be optionally designed by using the RIE process together with a mask or a laser photo-chemical etching process. The present invention can be applied to a tetrode type insulating gate device. Further, the present invention can be applicable to a silicon-on-silicon-on-silicon substrate or a monolithic multi-layer (for example, n-type three-layer) three-dimensional device prepared by a laser annealing. In Fig. 9, there is shown a further embodiment of a first semiconductor layer in a semiconductor device according to the present invention, having basically the same construction as that of the second embodiment, except a bipolar transistor instead of a MOS transistor. In this embodiment, in the front main surface, a p⁺-type base region 68 is formed in the surface portion of the n-type epitaxial layer 15 above the groove 13 of the p⁻-type semiconductor substrate 14, and an n⁺-type emitter region 69 is formed in the left side surface portion of the base region 68. An emitter electrode 70 is contacted to the surface of the emitter region 69, and a base electrode 71 is attached to the right side surface of the base region 68. An n⁺-type buried collector layer 72 is formed in the contact portion between the substrate 14 and the epitaxial layer 15, and the bottom of the buried collector layer 72 exposes to the bottom (the upper end in Fig. 9) of the groove 13 in the rear surface of the substrate 14. A collector electrode 73A is contacted to the bottom of the buried collector layer 72 at the bottom of the groove 13, and a rear surface contact terminal 73B is integrally connected to the collector electrode 73A in the similar manner to the contact portion 12A and the rear surface wiring 12B of the second embodiment shown in Fig. 2. A pair of p⁺-type separation regions 74 for separating the collector are formed in the epitaxial layer 15. In this embodiment, the same effects and advantages as those of the previous embodiments of the present invention can be obtained. It is readily understood that the present invention can be applicable to an integrated circuit including a bipolar transistor or a BiCMOS.

Claims: A semiconductor device comprising; a first semiconductor layer (1,2,3,14,15,23,51,101,103), having a plurality of grooves (13) formed in its rear surface and a plurality of active devices formed in the thin portions provided between the bottom of each groove and the opposite front surface of said first semiconductor layer, each active device having at least one electrode (8,9,21A,21B,61A,61B) at the front surface and at least one electrode (12A,B;73A) at the bottom of a corresponding groove (13), said at least one electrode at the bottom of said groove being integrally connected to a wiring portion (12B,73B) formed at the rear surface of said first semicondcutor layer outside said groove (13); and a second semiconductor layer (27,102) comprising semiconductor device structures (128,32) each having at least one electrode (46L,47L) on the surface facing the rear surface of the first semiconductor layer; said first and second semiconductor layers being stacked on one another such that at least one of said wiring portions (12B,73B) at the rear surface of the first semiconductor layer is electrically connected to at least one of the electrodes (46L,47L) on said second semiconductor layer. A semiconductor device according to claim 1, wherein at least one of said active devices in the first semiconductor layer has an active region (5) being contacted to both said at least one electrode (9) at the front surface of the first semiconductor layer and said at least one electrode (12A) at the bottom of the corresponding groove. A semiconductor device according to claim 1, wherein the at least one of said active devices in the first semiconductor layer has an active region being a buried portion (16,72) exposed at the bottom of the corresponding groove (13) and being contacted to said at least one electrode (72A,73A) at the bottom of the groove. A semiconductor device according to claim 1, wherein at least one of said active devices of said semiconductor layer is formed as a MOSFET or bipolar transistor. A semiconductor device according to claim 1, wherein at least one of said active devices in the first semiconductor layer has a low ohmic region (56) being contacted to both said at least one electrode at the front surface of the first semiconductor layer and said at least one electrode (12A) at the bottom of the corresponding groove, and being surrounded and thereby electrically isolated from the first semiconductor layer by isolating films (55).

Inventors: KOMIYA YOSHIO, KOMIYA, YOSHIO
Applicants: NISSAN MOTOR, NISSAN MOTOR CO., LTD.
Application year: 1988
Main classification: H01L23
IPC codes: H01L29, H01L23, H01L21