Patent Publication Number: US-2018047746-A1

Title: Semiconductor device and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 15/412,465 filed Jan. 23, 2017, which claims priority from Japanese Patent Application No. 2016-018589 filed on Feb. 3, 2016, the disclosures of which are incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a semiconductor device and a method of manufacturing the same, and can be used for manufacture of a semiconductor device which includes a low breakdown voltage transistor and a high breakdown voltage transistor, for example. 
     BACKGROUND OF THE INVENTION 
     A metal insulator semiconductor field effect transistor (MISFET or MIS field effect transistor) has been known as a semiconductor element which is used as a switching element or the like. Examples of the MISFET include a low breakdown voltage MISFET which is used in a peripheral circuit such as a logic circuit and a high breakdown voltage MISFET which is used in a memory cell or for input and output of power, and these MISFETs are consolidated in a single semiconductor chip in some cases. 
     Japanese Patent Application Laid-Open Publication No. 2004-349680 (Patent Document 1) and Japanese Patent Application Laid-Open Publication No. 2014-075557 (Patent Document 2) describe techniques of forming a relatively wide sidewall that covers sidewalls of a gate electrode of a transistor and a relatively narrow sidewall that covers sidewalls of a gate electrode of another transistor. 
     SUMMARY OF THE INVENTION 
     In the case of forming the low breakdown voltage MISFET and the high breakdown voltage MISFET on a semiconductor substrate, a method is considered in which a relatively wide sidewall is formed over sidewalls of gate electrodes of these MISFET&#39;s, and then, a relatively narrow sidewall is formed by reducing a width of the sidewall covering the sidewalls of the gate electrode of the low breakdown voltage MISFET using etching or the like. 
     However, when an interval between the gate electrodes of a plurality of the low breakdown voltage MISFET&#39;s, used in a logic circuit or the like, is reduced along with miniaturization of a semiconductor device, there is a risk that a gap between the gate electrodes is embedded by the sidewall at the time of forming the relatively wide sidewall. When the gap between the gate electrodes is embedded by the sidewall, it is difficult to reduce the width of the sidewall that covers the sidewalls of the gate electrodes of the low breakdown voltage MISFET using the etching or the like thereafter, which causes a problem that it is difficult to normally form the low breakdown voltage MISFET. 
     Other object and novel characteristics of the present invention will be apparent from the description of the present specification and the accompanying drawings. 
     The typical summary of the inventions disclosed in the present application will be briefly described as follows. 
     In a semiconductor device according to an embodiment, an insulating film, in contact with sidewalls of a metal gate electrode, is configured using a silicon nitride film. An insulating film, in contact with sidewalls of a charge storage film below a memory gate electrode of a split-gate type MONOS memory, is formed of a silicon oxide film. 
     In addition, in a method of manufacturing a semiconductor device according to another embodiment, a silicon nitride film and a first silicon oxide film are sequentially formed so as to cover each sidewall of a first gate electrode and a second gate electrode. Then, a first silicon oxide film covering the sidewall of the first gate electrode is removed. Thereafter, a second silicon oxide film covering the respective sidewalls of the first gate electrode and the second gate electrode is formed. Accordingly, a first sidewall including the silicon nitride film and the second silicon oxide film, which covers the sidewall of the first gate electrode, and a second sidewall including the silicon nitride film, the first silicon oxide film, and the second silicon oxide film, which cover the sidewall of the second gate electrode, are formed. 
     According to an embodiment, it is possible to improve the performance of the semiconductor device. 
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view during a process of manufacturing a semiconductor device according to a first embodiment; 
       FIG. 2  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 1 ; 
       FIG. 3  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 2 ; 
       FIG. 4  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 5 ; 
       FIG. 5  is a cross-sectional view illustrating a part of  FIG. 4  in an enlarged manner; 
       FIG. 6  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 5 ; 
       FIG. 7  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 6 ; 
       FIG. 8  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 7 ; 
       FIG. 9  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 8 ; 
       FIG. 10  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 9 ; 
       FIG. 11  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 10 ; 
       FIG. 12  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 11 ; 
       FIG. 13  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 12 ; 
       FIG. 14  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 13 ; 
       FIG. 15  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 14 ; 
       FIG. 16  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 15 ; 
       FIG. 17  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 16 ; 
       FIG. 18  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 17 ; 
       FIG. 19  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 18 ; 
       FIG. 20  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 19 ; 
       FIG. 21  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 20 ; 
       FIG. 22  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 21 ; 
       FIG. 23  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 22 ; 
       FIG. 24  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 23 ; 
       FIG. 25  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 24 ; 
       FIG. 26  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 25 ; 
       FIG. 27  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 26 ; 
       FIG. 28  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 27 ; 
       FIG. 29  is a cross-sectional view illustrating a part of  FIG. 28  in an enlarged manner; 
       FIG. 30  is a table illustrating an example of an application condition of a voltage to each portion of a selected memory cell during “programming”, “erase” and “read”; 
       FIG. 31  is a cross-sectional view during a process of manufacturing a modification example 1 of a semiconductor device according to a first embodiment; 
       FIG. 32  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 31 ; 
       FIG. 33  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 32 ; 
       FIG. 34  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 33 ; 
       FIG. 35  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 34 ; 
       FIG. 36  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 35 ; 
       FIG. 37  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 36 ; 
       FIG. 38  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 37 ; 
       FIG. 39  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 38 ; 
       FIG. 40  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 39 ; 
       FIG. 41  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 40 ; 
       FIG. 42  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 41 ; 
       FIG. 43  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 42 ; 
       FIG. 44  is a cross-sectional view illustrating a part of  FIG. 43  in an enlarged manner; 
       FIG. 45  is a cross-sectional view of a modification example 1 of a semiconductor device according to the first embodiment; 
       FIG. 46  is a cross-sectional view during a process of manufacturing a modification example 2 of a semiconductor device according to the first embodiment; 
       FIG. 47  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 46 ; 
       FIG. 48  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 47 ; 
       FIG. 49  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 48 ; 
       FIG. 50  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 49 ; 
       FIG. 51  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 50 ; 
       FIG. 52  is a cross-sectional view illustrating a part of  FIG. 51  in an enlarged manner; 
       FIG. 53  is a cross-sectional view during a process of manufacturing a semiconductor device according to a second embodiment; 
       FIG. 54  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 53 ; 
       FIG. 55  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 54 ; 
       FIG. 56  is a cross-sectional view illustrating a part of  FIG. 55  in an enlarged manner; 
       FIG. 57  is a cross-sectional view of the semiconductor device according to the second embodiment; 
       FIG. 58  is a cross-sectional view during a process of manufacturing a modification example 1 of a semiconductor device according to the second embodiment; 
       FIG. 59  is a cross-sectional view illustrating a part of  FIG. 58  in an enlarged manner; 
       FIG. 60  is a cross-sectional view during a process of manufacturing a modification example 2 of a semiconductor device according to the second embodiment; 
       FIG. 61  is a cross-sectional view illustrating a part of  FIG. 60  in an enlarged manner; 
       FIG. 62  is a cross-sectional view during a process of manufacturing a semiconductor device according to a Comparative Example; 
       FIG. 63  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 62 ; 
       FIG. 64  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 63 ; 
       FIG. 65  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 64 ; 
       FIG. 66  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 65 ; 
       FIG. 67  is a cross-sectional view during the process of manufacturing the semiconductor device continued from  FIG. 66 ; and 
       FIG. 68  is a cross-sectional view during a process of manufacturing a semiconductor device according to a Comparative Example. 
    
    
     DESCRIPTIONS OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout all the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Also, in the following embodiments, the description of the same or similar portion is not repeated in principle unless particularly required. 
     First Embodiment 
     A semiconductor device according to a first embodiment is a semiconductor device which is provided with a non-volatile memory (a non-volatile memory element, a flash memory, or a non-volatile semiconductor memory device). In the first embodiment and the following embodiments, the non-volatile memory will be described assuming a memory cell based on an n-channel MISFET. 
     In addition, polarities (a polarity of an applied voltage and a polarity of a carrier during program, erase and read) of the memory cell in the first embodiment and the following embodiments are given to describe an operation in the case of the memory cell based on the n-channel MISFET, and it is possible to obtain the same effect in principle when the memory cell is based on a p-channel MISFET by inverting the entire polarity of an applied potential and a conductivity type of the carrier. 
     &lt;Process of Manufacturing Semiconductor Device According to First Embodiment&gt; 
     Hereinafter, a description will be given regarding a method of manufacturing the semiconductor device according to the first embodiment with reference to  FIGS. 1 to 28 .  FIGS. 1 to 28  are cross-sectional views during a process of manufacturing the semiconductor device according to this embodiment.  FIGS. 1 to 4 , and  FIGS. 6 to 19  illustrate the cross-sectional views of a logic circuit region LP, a logic circuit region LN, an I/O region HV, and a memory cell region HM in this order from the left to the right of the drawings. These regions are delimited by the broken line in the drawings, and the respective regions are separated from each other. All the logic circuit regions LP and LN, the I/O region HV, and the memory cell region HM are present on a main surface of the same semiconductor substrate, and aligned with each other in a direction along the main surface.  FIG. 5  is the cross-sectional view illustrating a part of  FIG. 4  in an enlarged manner. 
     The logic circuit regions LP and LN and the I/O region HV are regions that form a peripheral circuit region. The peripheral circuit is a circuit excluding a non-volatile memory. The peripheral circuit is, for example, an input/output circuit, a power supply circuit or the like such as a control circuit, a sense amplifier, a column decoder, a row decoder, a module, or the like inside a memory module, and is a processor such as a CPU, various analog circuits, a memory module of static random access memory (SRAM), or an external input/output circuit outside the memory module. 
     The logic circuit region LP is a region that includes a p-channel MISFET having a low breakdown voltage to form the control circuit or the like. The logic circuit region LN is a region that includes an n-channel MISFET having a low breakdown voltage to form the control circuit or the like. The I/O region HV is a region that includes a p-channel MISFET having a high breakdown voltage to form a circuit, which performs input and output with respect to a device outside a semiconductor chip, or the power supply circuit. Here, the case of forming the p-channel MISFET in the I/O region HV is described, but the n-channel MISFET may be formed in the I/O region HV. 
     The memory cell region HM is a region for formation of a split-gate type metal oxide nitride oxide semiconductor (MONOS) memory. The MONOS memory is a non-volatile semiconductor memory device which is capable of electrically performing programming and erase, and includes a memory cell which is configured of two MISFETs that share source and drain regions with each other. The MONOS memory includes a trapping insulating film below a gate electrode of the MISFET, and is configured to set a charge storage state of the trapping insulating film as memory information and perform read using this information as a threshold of the transistor. The trapping insulating film indicates an insulating film (hereinafter, referred to as a charge storage film) which is capable of storing a charge, and examples thereof may include a silicon nitride film and the like. The memory is caused to operate as a memory element by shifting the threshold of the MISFET by injecting or releasing the charge into or from the charge storage region. 
     The MISFET, formed in each of the logic circuit regions LP and LN, is the low breakdown voltage MISFET that is driven with a lower voltage than the MISFET which is formed in each of the I/O region HV, and the memory cell region HM. 
     Examples of a method of forming a gate electrode of the logic circuit regions LP and LN include a method of using a so-called gate-last process in which a dummy gate electrode is formed on a substrate, and then, the dummy gate electrode is replaced with a metal gate electrode or the like. On the contrary, a description will be given herein regarding the case of using a gate-first process in which the metal gate electrode is formed from the beginning without providing the dummy gate electrode. Incidentally, the gate-last process will be described in Modification Examples 1 and 2 of this embodiment. In addition, a first method of forming an offset spacer will be described herein. 
     First, a semiconductor substrate SB, which includes the logic circuit regions LP and LN, the I/O region HV, and the memory cell region HM, is prepared in the process of manufacturing the semiconductor device according to the first embodiment as illustrated in  FIG. 1 . The semiconductor substrate SB is, for example, a monocrystalline silicon substrate. Subsequently, an element isolation region EI, which separates the logic circuit region LP, the logic circuit region LN, the I/O region HV, and the memory cell region HM from each other, is formed. The element isolation region EI is formed using an insulating film, which is embedded inside a trench formed in a main surface of the semiconductor substrate SB, and has a shallow trench isolation (STI) structure or a local oxidation of silicon (LOCOS) structure, for example. 
     Subsequently, wells NW 1 , PW 1 , NW 2  and PW 2  are formed in the main surface of the semiconductor substrate SB using a photolithography technique and an ion implantation method. The well NW 1  is formed by implanting n-type impurities (for example, phosphorus (P) or arsenic (As)) into the main surface of the semiconductor substrate SB in the logic circuit region LP. The well PW 1  is formed by implanting p-type impurities (for example, boron (B)) into the main surface of the semiconductor substrate SB in the logic circuit region LN. The well NW 2  is formed by implanting n-type impurities (for example, phosphorus (P) or arsenic (As)) into the main surface of the semiconductor substrate SB in the I/O region HV. The well PW 2  is formed by implanting p-type impurities (for example, boron (B)) into the main surface of the semiconductor substrate SB in the memory cell region HM. 
     Next, an insulating film IF 1  is formed on the main surface of the semiconductor substrate SB in the logic circuit regions LP and LN and the memory cell region HM, and an insulating film IF 2  is formed on the main surface of the semiconductor substrate SB in the I/O region HV as illustrated in  FIG. 2 . The insulating film IF 2  has a larger film thickness than the insulating film IF 1 . For example, the following method is used in the case of forming the insulating films having the two kinds of film thicknesses in this manner. That is, the insulating film IF 2 , which is thick and made of a silicon oxide film, is formed on the semiconductor substrate SB using a chemical vapor deposition (CVD) method, and then, the insulating film IF 2  except for the I/O region HV is removed by performing patterning using a photolithography technique and an etching method. Thereafter, the insulating film IF 1 , which is made of a silicon oxide film, is formed on the main surface of the semiconductor substrate SB in the logic circuit regions LP and LN and the memory cell region HM using, for example, a thermal oxidation method. 
     Although the description has been given regarding the case of forming the insulating film IF 1 , which has the same film thickness as the insulating film IF 1  in the logic circuit regions LP and LN, in the memory cell region HM here, an insulating film, which has a different film thickness from the insulating film IF 1  in the logic circuit regions LP and LN, may be formed on the main surface of the semiconductor substrate SB in the memory cell region HM. 
     Subsequently, a polysilicon film PS 1  and an insulating film IF 3  are sequentially formed on the main surface of the semiconductor substrate SB using, for example, a CVD method. The insulating film IF 3  is formed of, for example, a silicon nitride film. 
     Next, the insulating film IF 3 , the polysilicon film PS 1 , and the insulating films IF 1  and IF 2  in the I/O region HV and the memory cell region HM are patterned using a photolithography technique and a dry etching method as illustrated in  FIG. 3 . Accordingly, a gate insulating film GF 3 , formed using the insulating film IF 2 , and a gate electrode G 3 , formed using the polysilicon film PS 1  on the insulating film IF 2 , are formed in the I/O region HV, and a gate insulating film GF 4 , formed using the insulating film IF 1 , and a control gate electrode CG, formed using the polysilicon film PS 1  on the insulating film IF 1 , are formed in the memory cell region HM. Each upper surface of the gate electrode G 3  and the control gate electrode CG is covered by the insulating film IF 3 . Here, the logic circuit regions LP and LN are not subjected to patterning. 
     Next, an oxide nitride oxide (ONO) film ON and a polysilicon film PS 2  are formed on the main surface of the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 4 . As illustrated in  FIG. 5 , the ONO film ON is formed of a silicon oxide film (bottom oxide film) OX 1 , a silicon nitride film (charge storage film) NT 1 , and a silicon oxide film (top oxide film) OX 2  which are stacked in this order from the main surface side of the semiconductor substrate SB. The silicon oxide film OX 1  is formed using, for example, a thermal oxidation method, and the silicon nitride film NT 1  and the silicon oxide film OX 2  are formed using, for example, a CVD method. Although  FIGS. 4 and 6 to 28  illustrate the ONO film ON as a single film, the actual ONO film ON has a stacked structure as illustrated in  FIG. 5 . 
     Next, etchback (anisotropic etching) is performed to remove a part of the polysilicon film PS 2  and to cause an upper surface of the ONO film ON to be exposed as illustrated in  FIG. 6 . Accordingly, the polysilicon film PS 2  is left in a sidewall shape so as to cover each of sidewalls on both sides of the gate electrode G 3  and sidewalls on both sides of the control gate electrode CG with the ONO film ON interposed therebetween. Incidentally, the polysilicon film PS 2  that covers one sidewall of the control gate electrode CG forms a memory gate electrode MG. 
     Next, the polysilicon film PS 2  is removed while leaving the polysilicon film PS 2  that covers the one sidewall of the control gate electrode CG, that is, the memory gate electrode MG, as illustrated in  FIG. 7 , using a photolithography technique and a dry etching method. Subsequently, etching is performed using the memory gate electrode MG as a mask to remove the ONO film ON which is exposed from the memory gate electrode MG. Accordingly, the main surface of the semiconductor substrate SB and the surface of the insulating film IF 3  are exposed. 
     Next, an interlayer insulating film IL 1 , made of a silicon oxide film, is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method, then, an upper surface of the interlayer insulating film IL 1  is polished using a chemical mechanical polishing (CMP) method, thereby causing an upper surface of the insulating film IF 3  to be exposed as illustrated in  FIG. 8 . 
     Next, an insulating film IF 4  is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method, and then, the insulating film IF 4  in the logic circuit regions LP and LN is removed using a photolithography technique and an etching method as illustrated in  FIG. 9 . At this time, the interlayer insulating film IL 1  and the insulating film IF 3  in the I/O region HV and the memory cell region HM remain in the state of being covered by the insulating film IF 4 . The insulating film IF 4  is made of a material which is different from that of the insulating film IF 3  serving as a cap insulating film, and is made of, for example, silicon oxide. 
     Next, etching is performed using the insulating film IF 4  as a mask to remove the insulating film IF 3  in the logic circuit regions LP and LN, and thereafter, the polysilicon film PS 1  and the insulating film IF 1  in the logic circuit regions LP and LN are removed as illustrated in  FIG. 10 . Incidentally, the insulating film IF 1  may be left without being removed. The insulating film IF 3 , the gate electrode G 3 , the control gate electrode CG, the memory gate electrode MG, and the like in the I/O region HV and the memory cell region HM are protected by the insulating film IF 4 , and thus, are not removed when the insulating film IF 3 , the polysilicon film PS 1 , and the insulating film IF 1  in the logic circuit regions LP and LN are removed as above. 
     Next, the insulating film IF 4  in the I/O region HV and the memory cell region HM are removed as illustrated in  FIG. 11 . Subsequently, an insulating film HK, a metal film MF, and a polysilicon film PS 3  are sequentially formed on the main surface of the semiconductor substrate SB. Incidentally, the insulating film HK, the metal film MF, and the polysilicon film PS 3  may be sequentially formed after forming an insulating film, made of a silicon oxide film, for example, on the semiconductor substrate SB using an oxidation method or a CVD method when the insulating film IF 1  has been removed in the process that has been described with reference to  FIG. 10 . 
     The insulating film HK is a so-called high-k film (high dielectric constant film) which is an insulating material film having a higher dielectric constant (relative dielectric constant) than silicon nitride. Examples of the insulating film HK may include metal oxide films such as a hafnium oxide film, a zirconium oxide film, an aluminum oxide film, a tantalum oxide film and a lanthanum oxide film, and further, these metal oxide films may further contain one of nitrogen (N) and silicon (Si) or the both. It is possible to increase a physical film thickness of a gate insulating film in the case of using the high dielectric constant film (herein, the insulating film HK) as the gate insulating film than the case of using a silicon oxide film, and thus, it is possible to obtain an advantage that a leakage current can be reduced. The insulating film HK and the polysilicon film PS 3  can be formed using, for example, CVD. 
     Examples of the metal film MF may include metal films such as a titanium nitride (TiN) film, a tantalum nitride (TaN) film, a tungsten nitride (WN) film, a titanium carbide (TiC) film, a tantalum carbide (TaC) film, a tungsten carbide (WC) film, a nitride tantalum carbide (TaCN) film, a titanium (Ti) film, a tantalum (Ta) film, and a titanium aluminum (TiAl) film. Incidentally, the metal film described herein indicates a conductive film having metal conductivity, and is assumed to include not only a single metal film (pure metal film) or an alloy film but also a metal compound film (such as a metal nitride film and a metal carbide film) having metal conductivity. 
     The metal film MF can be formed using, for example, a sputtering method or the like. The metal film MF may have a configuration in which a plurality of metal films, made of different materials, among the above-described metal films made of various materials are stacked. For example, the metal film MF may be a stacked film in which a titanium film is stacked on a titanium nitride film. 
     The metal film MF forms a gate electrode of the low breakdown voltage MISFET, which will be formed in the subsequent process, and the gate electrode including the metal film MF will be referred to as a metal gate electrode, hereinafter. The MISFET using the metal gate electrode has an advantage that it is possible to suppress a depletion phenomenon of the gate electrode and eliminate a parasitic capacitance. In addition, it is also possible to obtain reduction in size of an MISFET element (reduction in thickness of the gate insulating film). 
     Next, the polysilicon film PS 3 , the metal film MF, and the insulating film HK are patterned using a photolithography technique and a dry etching method as illustrated in  FIG. 12 . Accordingly, a gate insulating film GF 1 , formed using the insulating film HK, and a gate electrode G 1 , which is the metal gate electrode formed using the polysilicon film PS 3  and the metal film MF on the insulating film HK, are formed in the logic circuit region LP, and a gate insulating film GF 2 , formed using the insulating film HK, and a gate electrode G 2 , which is the metal gate electrode formed using the polysilicon film PS 3  and the metal film MF on the insulating film HK, are formed in the logic circuit region LN. In addition, the polysilicon film PS 3 , the metal film MF, and the insulating film HK are removed, and each upper surface of the interlayer insulating film IL 1  and the insulating film IF 3  are exposed in the I/O region HV and the memory cell region HM. 
     Subsequently, the interlayer insulating film IL 1  in the I/O region HV and the memory cell region HM is removed using a wet etching method. In the above-described manner, the metal gate electrode and another gate electrode made of the polysilicon film are formed according to the gate-first process. Hereinafter, the first method of forming the offset spacer will be described with reference to  FIGS. 13 to 19 . 
     Next, a photoresist film PR 1  is formed on the main surface of the semiconductor substrate SB so as to cover the entire main surface thereof except for the I/O region HV, and then, a pair of extension regions EX 3  is formed on the main surface of the semiconductor substrate SB in the I/O region HV by performing ion implantation using the photoresist film PR 1  and the insulating film IF 3  as a mask as illustrated in  FIG. 13 . The extension region EX 3  is a p-type semiconductor region which is formed by implanting p-type impurities (for example, boron (B)) into the main surface of the semiconductor substrate SB at both lateral sides of the gate electrode G 3  at a relatively low concentration. 
     Next, the photoresist film PR 1  is removed, then, a photoresist film PR 2  is formed on the main surface of the semiconductor substrate SB so as to cover the entire main surface thereof except for the memory cell region HM, and thereafter, a pair of extension regions EX 4  is formed on the main surface of the semiconductor substrate SB in the memory cell region HM by performing ion implantation using the photoresist film PR 2 , the memory gate electrode MG, the ONO film ON, and the insulating film IF 3  as a mask as illustrated in  FIG. 14 . The extension region EX 4  is an n-type semiconductor region which is formed by implanting n-type impurities (for example, phosphorus (P) or arsenic (As)) into the main surface of the semiconductor substrate SB at both sides of a film pattern including the control gate electrode CG, the memory gate electrode MG, and the ONO film ON at a relatively low concentration. 
     Next, the photoresist film PR 2  is removed, and then, a silicon oxide film OX 3  is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 15 . Accordingly, the main surface of the semiconductor substrate SB and sidewalls and upper surfaces of the gate electrodes G 1  to G 3  are covered by the silicon oxide film OX 3 . In addition, sidewalls and an upper surface of the pattern including the control gate electrode CG, the memory gate electrode MG, and the ONO film ON are also covered by the silicon oxide film OX 3 . A film thickness of the silicon oxide film OX 3  is, for example, 5 nm. In the present application, the film thickness indicates a length of a film in a direction vertical to a base face of the deposited film. Accordingly, for example, the sidewalls of the gate electrode G 3  are formed along the direction vertical to the main surface of the semiconductor substrate SB, and the film thickness of the silicon oxide film OX 3  that covers the corresponding sidewalls indicates a length of the silicon oxide film OX 3  in the direction vertical to the corresponding sidewalls. 
     Next, a photoresist film PR 3  is formed so as to cover the entire main surface except for the logic circuit region LN, and then, a pair of extension regions EX 2  is formed on the main surface of the semiconductor substrate SB in the logic circuit region LN by performing ion implantation using the photoresist film PR 3  and the polysilicon film PS 3  as a mask as illustrated in  FIG. 16 . The extension region EX 2  is an n-type semiconductor region which is formed by implanting n-type impurities (for example, phosphorus (P) or arsenic (As)) into the main surface of the semiconductor substrate SB at both lateral sides of the gate electrode G 2  at a relatively low concentration. In this ion implantation, impurity ions are implanted into the main surface of the semiconductor substrate SB penetrating the silicon oxide film OX 3 . 
     Next, the photoresist film PR 3  is removed, and then, a silicon nitride film NT 2  is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 17 . Accordingly, a surface of the silicon oxide film OX 3  is covered by the silicon nitride film NT 2 . A film thickness of the silicon nitride film NT 2  is, for example, 5 nm. Subsequently, etchback is selectively performed using a dry etching method to remove a part of the silicon nitride film NT 2  so that a partial surface of the silicon oxide film OX 3  is exposed. At this time, the silicon oxide film OX 3  can be used as an etching stopper film, and thus, it is possible to perform highly accurate etching. 
     The silicon nitride film NT 2  is left in a sidewall shape so as to cover each of the sidewalls of the gate electrodes G 1  to G 3 , one sidewall of the control gate electrode CG, and one sidewall of the memory gate electrode MG. Accordingly, an offset spacer OS 1 , which is formed of the silicon oxide film OX 3  and the silicon nitride film NT 2 , is formed. 
     Next, a photoresist film PR 4  is formed so as to cover the entire main surface except for the logic circuit region LP, and then, a pair of extension regions EX 1  is formed on the main surface of the semiconductor substrate SB in the logic circuit region LP by performing ion implantation using the photoresist film PR 4  and the polysilicon film PS 3  as a mask as illustrated in  FIG. 18 . The extension region EX 1  is a p-type semiconductor region which is formed by implanting p-type impurities (for example, boron (B)) into the main surface of the semiconductor substrate SB at both lateral sides of the gate electrode G 1  at a relatively low concentration. In this ion implantation, impurity ions are implanted into the main surface of the semiconductor substrate SB penetrating the silicon oxide film OX 3 . 
     Next, the photoresist film PR 4  is removed as illustrated in  FIG. 19 . 
     Hereinafter, a description will be given regarding a method of forming a sidewall, which is one of the main characteristics of this embodiment, with reference to  FIGS. 20 to 24 .  FIGS. 20 to 28  and  FIG. 29 , which will be used in the subsequent description, do not illustrate the above-described silicon oxide film OX 3 , which is formed along each upper surface of the gate electrodes and the main surface of the semiconductor substrate SB. In addition,  FIGS. 20 to 28  illustrate the offset spacer OS 1  as a single film in order to facilitate understanding of the drawings. That is, the silicon oxide film OX 3  and the silicon nitride film NT 2  which form the offset spacer OS 1  are not distinguished from each other. 
     In addition,  FIGS. 20 to 29  only illustrate the logic circuit region LN and the memory cell region HM without description regarding the manufacturing process in the logic circuit region LP and the I/O region HV. The manufacturing process in the logic circuit region LP is performed in the same manner as in the logic circuit region LN, and the manufacturing process in the I/O region HV is performed in the same manner as in the memory cell region HM. However, the p-type impurities are injected in the ion implantation process, which is performed to form a diffusion layer forming source and drain regions, in each of the manufacturing processes in the logic circuit region LP and the I/O region HV, which is different from that in the logic circuit region LN and the memory cell region HM. In addition,  FIGS. 20 to 28  illustrate cross-sectional views of the case of forming two MISFETs side by side in the logic circuit region LN. 
     Next, a silicon nitride film NT 3  and a silicon oxide film OX 4  are sequentially formed on the main surface of the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 20 . Here, a distance between the neighboring gate electrodes G 2  in the logic circuit region LN is, for example, 90 nm in the case of ignoring a film thickness of the offset spacer OS 1 . A distance between the offset spacers OS 1 , which cover the respective opposing sidewalls of the neighboring gate electrodes G 2 , is 90 nm in the case of considering the film thickness of the offset spacer OS 1 . 
     In these cases, it is necessary to prevent the gap between the neighboring gate electrodes G 2  from being completely embedded by the silicon nitride film NT 3  and the silicon oxide film OX 4  in order to prevent occurrence of failure during a process of removing the silicon nitride film NT 3  and the silicon oxide film OX 4 , which is performed in the subsequent process. That is, a film thickness of the stacked film, formed of the silicon nitride film NT 3  and the silicon oxide film OX 4 , needs to be smaller than a half value of 90 nm. Here, a distance between the neighboring gate electrodes G 2  is greater than twice a total film thickness of the silicon nitride film NT 3  and the silicon oxide film OX 4 . Accordingly, when a film thickness of the silicon nitride film NT 3  is set as “a” and a film thickness of the silicon oxide film OX 4  is set as “b”, a+b&lt;45 (nm). In other words, 2a+2b&lt;90 (nm). 
     Here, the film thickness a of the silicon nitride film NT 3  is, for example, 15 nm, and the film thickness a of the silicon oxide film OX 4  is, for example, 20 nm. The film thickness b of the silicon nitride film NT 3  needs to have a dimension at a level that does not expose the main surface of the semiconductor substrate SB in an etchback process (see  FIG. 21 ), which is performed after processing the silicon oxide film OX 4  in a sidewall shape, and thus, requires a dimension of, for example, 10 nm or larger. 
     Incidentally, a plurality of the patterns, each of which includes the control gate electrode CG and the memory gate electrode MG adjacent to each other, are formed in the memory cell region HM, and a distance between the patterns is larger than 90 nm. Thus, when the gap between the gate electrodes G 2  in the logic circuit region LN is not completely embedded by the silicon nitride film NT 3  and the silicon oxide film OX 4 , a gap between the above-described patterns is also not completely embedded. In addition, here, the case of being “completely embedded” indicates a casein which films that are formed, respectively, along the two sidewalls, which oppose each other, of the gate electrode are in contact with each other. 
     Next, etchback is selectively performed using a dry etching method to remove a part of the silicon oxide film OX 4  so that an upper surface of the silicon nitride film NT 3  is exposed as illustrated in  FIG. 21 . At this time, the silicon nitride film NT 3  functions as an etching stopper film. Through this the etchback process, the silicon oxide film OX 4  is left in the sidewall shape. 
     Next, a photoresist film PR 5  is formed to cover the memory cell region HM and to expose the logic circuit region LN, and the silicon oxide film OX 4  in the logic circuit region LN is removed using wet etching as illustrated in  FIG. 22 . 
     Next, the photoresist film PR 5  is removed, and then, a silicon oxide film OX 5  is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 23 . Here, a film thickness of the silicon oxide film OX 5  is set as “c”. The film thickness c of the silicon oxide film OX 5  is, for example, 11 nm. Accordingly, the gap between the gate electrodes G 2  is not completely embedded by the silicon nitride film NT 3  and the silicon oxide film OX 5 . The silicon oxide film OX 5  covers the gate electrode G 2  and the silicon nitride film NT 3  in the logic circuit region LN, and covers the control gate electrode CG, the memory gate electrode MG, the silicon nitride film NT 3 , and the silicon oxide film OX 4  in the memory cell region HM. In addition, the silicon oxide film OX 5  covers the main surface of the semiconductor substrate SB. 
     Next, etchback is performed using a dry etching method to remove a part of the silicon oxide film OX 5 , and thereafter, the silicon nitride film NT 3 , which is exposed from the silicon oxide films OX 4  and OX 5 , is removed as illustrated in  FIG. 24 . Accordingly, a sidewall SW 1  is formed along the sidewalls of the gate electrode G 2  in the logic circuit region LN with the offset spacer OS 1  interposed therebetween. The sidewall SW 1  is formed of the silicon nitride film NT 3  and the silicon oxide film OX 5 . In addition, a sidewall SW 2  is formed along the sidewalls of the pattern, which includes the control gate electrode CG and the memory gate electrode MG adjacent to each other, in the memory cell region HM with the offset spacer OS 1  interposed therebetween the sidewall SW 2 . The sidewall SW 2  is formed of the silicon nitride film NT 3 , and the silicon oxide films OX 4  and OX 5 . 
     A film thickness of the sidewall SW 1 , that is, a width dimension in a direction along the main surface of the semiconductor substrate SB is 26 nm which is obtained by adding the film thickness a of the silicon nitride film NT 3  and the film thickness c of the silicon oxide film OX 5 . On the other hand, a film thickness of the sidewall SW 2 , that is, a width dimension in a direction along the main surface of the semiconductor substrate SB is 46 nm which is obtained by adding the film thickness a of the silicon nitride film NT 3 , the film thickness b of the silicon oxide film OX 4 , and the film thickness c of the silicon oxide film OX 5 . 
     Accordingly, the width (film thickness) of the sidewall SW 2  is larger than the width (film thickness) of the sidewall SW 1 . One of the main characteristics of the first embodiment is to separately form the plurality of sidewalls SW 1  and SW 2  which have different film thicknesses as above. In addition, another one of the main characteristics of the first embodiment is that the width dimension of the sidewall SW 2  is equal to or larger than a half of the distance between the neighboring gate electrodes G 2 . Incidentally, each gap among the above-described plurality of patterns in the memory cell region HM is not completely embedded even in the case of forming the sidewall SW 2  having the width of 46 nm. Incidentally, any width used in the present application indicates a length in a direction along the main surface of the semiconductor substrate SB. 
     One sidewall of the control gate electrode CG is covered by the sidewall SW 2 , and the other sidewall of the control gate electrode CG is covered by the sidewall SW 2  with the memory gate electrode MG interposed therebetween. In addition, one sidewall of the memory gate electrode MG is covered by the sidewall SW 2 , and the other side wall of the memory gate electrode MG is covered by the sidewall SW 2  with the control gate electrode CG interposed therebetween. 
     Next, a diffusion layer DF 2  is formed on the main surface of the semiconductor substrate SB in the logic circuit region LN, and a diffusion layer DF 4  is formed on the main surface of the semiconductor substrate SB in the memory cell region HM by performing ion implantation using the sidewalls SW 1  and SW 2 , the offset spacer OS 1 , the gate electrode G 2 , the insulating film IF 3 , the ONO film ON, and the memory gate electrode MG as a mask as illustrated in  FIG. 25 . Accordingly, a MISFET Q 2 , which is formed of the gate electrode G 2 , the extension region EX 2 , and the diffusion layer DF 2  and includes source and drain regions, is formed in the logic circuit region LN. In addition, a memory cell MC, which is formed of the control gate electrode CG, the memory gate electrode MG, the ONO film ON, the extension region EX 4 , and the diffusion layer DF 4 , and includes source and drain regions, is formed in the memory cell region HM. 
     Although the description has been given here regarding the case of forming the diffusion layers DF 2  and DF 4  using one-time ion implantation, the diffusion layer DF 2  and the diffusion layer DF 4  may be formed using different ion implantation processes, and each impurity concentration of the diffusion layers may be set to be different. In addition, the diffusion layer DF 4  on the source region side and the diffusion layer DF 4  on the drain region side to be formed in the memory cell region HM may be formed using different ion implantation processes, and each impurity concentration of these diffusion layers DF 4  may be set to be different. 
     In the memory cell region HM, the source and drain regions and the control gate electrode CG form a control transistor, and the source and drain regions and the memory gate electrode MG form a memory transistor. The memory cell MC is configured of the control transistor and the memory transistor. Each of the control transistor and the memory transistor is the transistor that is driven with a higher voltage than the MISFET Q 2 . That is, the MISFET Q 2  is a low breakdown voltage MISFET, and each of the control transistor and the memory transistor is a high breakdown voltage MISFET. Incidentally, a transistor including the gate electrode G 3  (see  FIG. 19 ) formed in the I/O region HV (not illustrated) is a high breakdown voltage transistor which is driven with a higher voltage than the MISFET Q 2 . 
     The diffusion layer DF 2  is an n-type semiconductor region which is formed by implanting n-type impurities (for example, phosphorus (P) or arsenic (As)) into the main surface of the semiconductor substrate SB at both lateral sides of the gate electrode G 2  at a relatively high concentration. The diffusion layer DF 4  is an n-type semiconductor region which is formed by implanting n-type impurities (for example, phosphorus (P) or arsenic (As)) into the main surface of the semiconductor substrate SB at both lateral sides of the above-described pattern including the control gate electrode CG and the memory gate electrode MG at a relatively high concentration. 
     Each of the diffusion layers DF 2  and DF 4  has a higher impurity concentration than the extension regions EX 2  and EX 4 . That is, the source and drain regions formed using the extension region EX 2  and the diffusion layer DF 2  and the source and drain regions formed using the extension region EX 4  and the diffusion layer DF 4  have a structure in which a semiconductor region having a low concentration and a semiconductor region having a high concentration are adjacent to each other, that is, a lightly doped drain (LDD) structure. In addition, the diffusion layers DF 2  and DF 4  are formed to be deeper than the extension regions EX 2  and EX 4 . The extension region EX 2  is formed to be closer to the main surface of the semiconductor substrate SB, which is right below the gate electrode G 2 , that is, a region in which a channel is formed than the diffusion layer DF 2 . Incidentally, the diffusion layers DF 2  and DF 4  may be formed to be shallower than the extension regions EX 2  and EX 4 . 
     Next, a silicide layer S 1  is formed on a silicon surface, which is exposed on the main surface of the semiconductor substrate SB, using a known salicide technique as illustrated in  FIG. 26 . That is, a metal film is deposited on the main surface of the semiconductor substrate SB using, for example, a sputtering method, then, heat treatment is performed to cause reaction between the metal film and the above-described silicon so as to form the silicide layer S 1 , and subsequently, an unreacted part of the metal film is removed using wet etching. Accordingly, the silicide layer S 1 , which forms each upper surface of the diffusion layers DF 2  and DF 4 , the gate electrode G 2 , and the memory gate electrode MG, is formed. Incidentally, the insulating film IF 3  on the control gate electrode CG has been removed before the formation of the silicide layer S 1  in a power supply portion (not illustrated) of the control gate electrode CG, and the silicide layer S 1 , which forms the upper surface of the control gate electrode CG, is formed in the power supply portion. 
     The silicide layer S 1  is made of, for example, a cobalt silicide layer, a nickel silicide layer, or a nickel-platinum silicide layer. The above-described metal film is made of a cobalt (Co) film, a nickel (Ni) film, or a nickel-platinum alloy film. 
     Subsequently, an etching stopper film (not illustrated) and an interlayer insulating film IL 2  are sequentially formed on the main surface of the semiconductor substrate SB using, for example, a CVD method to cover the MISFET Q 2  and the memory cell MC. The etching stopper film is made of, for example, a silicon nitride film. The interlayer insulating film IL 2  is made of, for example, a silicon oxide film, and a film thickness thereof is larger than a film thickness of a stacked film including the gate insulating film GF 4 , the control gate electrode CG, and the insulating film IF 3 . Thereafter, an upper surface of the interlayer insulating film IL 2  is planarized using, for example, a CMP method. 
     Next, a plurality of contact holes CH are formed to penetrate between the upper surface and a lower surface of the interlayer insulating film IL 2  using a photolithography technique and a dry etching method as illustrated in  FIG. 27 . An upper surface of the silicide layer S 1 , which covers each upper surface of the respective gate electrodes and the respective source and drain regions, is exposed on a bottom portion of the contact hole CH. 
     Next, a contact plug (connection portion) CP is formed to be embedded inside the contact hole CH as illustrated in  FIG. 28 . Thereafter, a wiring layer, which includes a wiring electrically connected to the contact plug CP, is formed on the contact plug CP, although not illustrated, and accordingly, the semiconductor device according to the first embodiment is completed. The contact plug CP is made mainly of, for example, a tungsten (W) film. 
     When the contact plug CP is formed, for example, a barrier conductor film (not illustrated) and a main conductor film (tungsten film) are first formed sequentially on the main surface of the semiconductor substrate SB using, for example, a sputtering method so that the inside of the contact hole CH is completely embedded. Thereafter, the barrier conductor film and the main conductor film remaining on the interlayer insulating film IL 2  are removed using a CMP method or the like to expose the upper surface of the interlayer insulating film IL 2 , thereby forming the contact plug CP which is formed of the barrier conductor film and the main conductor film that remain inside the contact hole CH. The contact plug CP is electrically connected to the respective source and drain regions, the gate electrode G 1  (not illustrated), the gate electrode G 2 , the gate electrode G 3  (not illustrated), the control gate electrode CG, or the memory gate electrode MG via the silicide layer S 1 . 
       FIG. 29  illustrates a cross-sectional view of the MISFET Q 2  and the memory cell MC, which are formed through the above-described manufacturing process in an enlarged manner. That is,  FIG. 29  is the cross-sectional view illustrating a part of  FIG. 28  in an enlarged manner.  FIG. 29  illustrates the stacked structure of the ONO film ON and the stacked structure of the offset spacer OS 1  in detail. In addition,  FIG. 29  does not illustrate the silicide layer S 1 , the interlayer insulating film IL 2 , and the contact plug CP. 
     As illustrated in  FIG. 29 , the silicon oxide film OX 3  forming the offset spacer OS 1  is in contact with a sidewall of the silicon nitride film NT 1  forming the ONO film ON. In addition, the ONO film ON is interposed between the control gate electrode CG and the memory gate electrode MG neighboring each other, and the corresponding ONO film ON is interposed between the memory gate electrode MG and the semiconductor substrate SB. That is, the ONO film ON has an L-like cross-sectional shape and is formed continuously from a portion between the control gate electrode CG and the memory gate electrode MG over a portion between the memory gate electrode MG and the semiconductor substrate SB. 
     &lt;Regarding Operation of Non-Volatile Memory&gt; 
     Next, an operation example of the non-volatile memory will be described with reference to  FIG. 30 . 
     The memory cell of the first embodiment has a MISFET structure and is configured to set a charge storage state of a trapping insulating film inside a gate electrode of the MISFET as memory information and to read the information as a threshold of the transistor. The trapping insulating film indicates an insulating film which is capable of storing a charge, and examples thereof may include a silicon nitride film and the like. The memory cell is caused to operate as a memory element by shifting the threshold of the MISFET by injecting or releasing the charge into or from such a charge storage region. Examples of the non-volatile semiconductor memory device that uses the trapping insulating film may include the split-gate type MONOS memory like the memory cell according to this embodiment. 
       FIG. 30  is a table illustrating an example of an application condition of a voltage to each portion of a selected memory cell during “programming”, “erase” and “read” according to this embodiment. In the table of  FIG. 30 , a voltage Vmg to be applied to the memory gate electrode MG of the memory cell MC as illustrated in  FIG. 29 , a voltage Vs to be applied to the source region, a voltage Vcg to be applied to the control gate electrode CG, a voltage Vd to be applied to the drain region, and a base voltage Vb to be applied to the well PW 2  in the upper surface of the semiconductor substrate SB are described each case of “programming”, “erase” and “read”. The selected memory cell used here indicates a memory cell which is selected as a target to perform “programming”, “erase” or “read”. 
     Incidentally, an active region on the right of the memory gate electrode MG is the source region and an active region on the left of the control gate electrode CG is the drain region in the example of the non-volatile memory illustrated in  FIG. 29 . In addition, the table illustrated in  FIG. 30  is a preferred example of the application condition of the voltage, and the invention is not limited thereto but various modifications can be made if necessary. In addition, the injection of electrons into the silicon nitride film NT 1  serving as a charge storage portion in the ONO film ON of the memory transistor is defined as “programming”, and the injection of holes is defined as “erase” in this embodiment. 
     In addition, a field A in the table of  FIG. 30  corresponds to a case in which a programming method is an SSI method and an erase method is a BTBT method, a field B corresponds to a case in which the programming method is the SSI method and the erase method is an FN method, a field C corresponds to a case in which the programming method is the FN method and the erase method is the BTBT method, and a field D corresponds to a case in which the programming method is the FN method and the erase method is the FN method. 
     The SSI method can be considered as an operation method in which programming of the memory cell is performed by injecting hot electrons into the silicon nitride film NT 1 , the BTBT method can be considered as an operation method in which erase of the memory cell is performed by injecting hot holes into the silicon nitride film NT 1 , and the FN method can be considered as an operation method in which programming or erase is performed using tunneling of electrons or holes. When the FN method is described in other words, programming in the FN method can be considered as an operating method in which programming of the memory cell is performed by injecting electrons into the silicon nitride film NT 1  using an FN tunnel effect, erase in the FN method can be considered as an operating method in which erase of the memory cell is performed by injecting holes into the silicon nitride film NT 1  using the FN tunnel effect. Hereinafter, these methods will be described in detail. 
     The programming method includes a programming method (hot electron injection programming method) in which programming is performed by injecting hot electrons using source side injection, that is, the so-called SSI method and a programming method (tunneling programming method) in which programming is performed using a Fowler Nordheim (FN) tunneling, that is, the so-called FN method. 
     During programming in the SSI method, for example, voltages (Vmg=10 V, Vs=5 V, Vcg=1 V, Vd=0.5 V, Vb=0 V) shown in “programming operation voltages” in the field A or the field B of the table of  FIG. 30  are applied to each portion of the selected memory cell to which the programming is performed, and the programming is performed by injecting electrons into the silicon nitride film NT 1  in the ONO film ON of the selected memory cell. 
     At this time, hot electrons are generated in a channel region (between the source and the drain) below the portion between the two gate electrodes (the memory gate electrode MG and the control gate electrode CG), and the hot electrons are injected into the silicon nitride film NT 1  serving as the charge storage portion in the ONO film ON below the memory gate electrode MG. The injected hot electrons (electrons) are trapped in a trap level of the silicon nitride film NT 1  of the ONO film ON, and as a result, a threshold voltage of the memory transistor increases. That is, the memory transistor is turned into a programming state. 
     During programming in the FN method, for example, voltages (Vmg=−12 V, Vs=0 V, Vcg=0 V, Vd=0 V, Vb=0 V) shown in “programming operation voltages” in the field C or the field D of the table of  FIG. 30  are applied to each portion of the selected memory cell to which the programming is performed, and the programming is performed in the selected memory cell by tunneling electrons from the memory gate electrode MG and injecting the electrons into the silicon nitride film NT 1  of the ONO film ON. At this time, the electrons are injected into the ONO film ON through tunneling of the silicon oxide film OX 2  from the memory gate electrode MG according to the FN tunneling (FN tunnel effect), and are trapped in the trap level in the silicon nitride film NT 1  of the ONO film ON, and as a result, the threshold voltage of the memory transistor increases. That is, the memory transistor is turned into the programming state. 
     Incidentally, it is also possible to perform programming by tunneling electrons from the semiconductor substrate SB and injecting the electrons into the silicon nitride film NT 1  of the ONO film ON during the programming in the FN method. In this case, it is possible to apply programming operation voltages by inverting each polarity of “programming operation voltages” in the field C or the field D of the table of  FIG. 30 , for example. 
     The erase method includes an erase method (hot hole injection erase method) in which erase is performed by injecting hot holes using a band-to-band tunneling (BTBT) phenomenon, that is, the so-called BTBT method and an erase method (tunneling erase method) in which erase is performed using the FN tunneling, that is, the so-called FN method. 
     During erase in the BTBT method, the erase is performed by injecting holes, generated through the BTBT phenomenon, into the charge storage section (the silicon nitride film NT 1  of the ONO film ON). For example, voltages (Vmg=−6 V, Vs=6 V, Vcg=0 V, Vd=open, Vb=0 V) shown in “erase operation voltages” in the field A or the field C of the table of  FIG. 30  are applied to each portion of the selected memory cell to which the erase is performed. Accordingly, holes are generated using the BTBT phenomenon and accelerated under an electric field so that the holes are injected into the silicon nitride film NT 1  in the ONO film ON of the selected memory cell, and accordingly, the threshold voltage of the memory transistor is decreased. That is, the memory transistor is turned into an erase state. 
     During erase in the FN method, for example, voltages (Vmg=12 V, Vs=0 V, Vcg=0 V, Vd=0 V, Vb=0 V) shown in “erase operation voltages” in the field B or the field D of the table of  FIG. 30  are applied to each portion of the selected memory cell to which the erase is performed. Then, the erase is performed in the selected memory cell by tunneling holes from the memory gate electrode MG and injecting the holes into the silicon nitride film NT 1  of the ONO film ON. At this time, the holes are injected into the ONO film ON through tunneling of the silicon oxide film OX 2  from the memory gate electrode MG according to the FN tunneling (FN tunnel effect), and are trapped in the trap level in the silicon nitride film NT 1  of the ONO film ON, and as a result, the threshold voltage of the memory transistor decreases. That is, the memory transistor is turned into the erase state. 
     Incidentally, it is also possible to perform the erase by tunneling holds from the semiconductor substrate SB and injecting the holes into the silicon nitride film NT 1  of the ONO film ON during the erase in the FN method. In this case, it is possible to apply erase operation voltages by inverting each polarity of “erase operation voltages” in the field B or the field D of the table of  FIG. 30 , for example. 
     During read, for example, voltages shown in “read operation voltages” in the field A, the field B, the field C or the field D of the table of  FIG. 30  are applied to each portion of the selected memory cell to which the read is performed. When the voltage Vmg to be applied to the memory gate electrode MG during the read is set to be a value between the threshold voltage of the memory transistor in the programming state and the threshold voltage thereof in the erase state, it is possible to determine whether the memory transistor is in the programming state or the erase state. 
     &lt;Regarding Effect of First Embodiment&gt; 
     Hereinafter, a problem of a semiconductor device according to a comparative example will be described with reference to  FIGS. 62 to 68 , and effects of the semiconductor device according to the first embodiment and the manufacturing method thereof will be described with reference to  FIG. 29  and the like.  FIGS. 62 to 68  are cross-sectional views during a process of manufacturing the semiconductor device according to the comparative example, and are the cross-sectional view illustrating the logic circuit region LN and the memory cell MC similarly to  FIGS. 20 to 28 . 
     A transistor forming a logic circuit is driven with a lower voltage than a transistor to be formed in an I/O region or a memory cell region, and thus, a high breakdown voltage performance is not required. Thus, a risk that punch-through occurs between source and drain regions is lower in a low breakdown voltage MISFET forming the logic circuit than in a high breakdown voltage transistor to be formed in the I/O region or the memory cell region, and a leakage current is hardly generated between the drain region and the gate electrode. Accordingly, it is possible to realize improvement in integration degree, low power consumption and high-speed operation of elements in the low breakdown voltage MISFET in a relatively easy manner by reducing an interval between the source and drain regions. 
     There is a method of reducing a width of a sidewall to be used as a mask for ion implantation at the time of forming a diffusion layer forming the source and drain regions as a method of reducing of the distance between the source and drain regions in order to form such a low breakdown voltage MISFET. However, the high breakdown voltage MISFET such as a memory cell requires a higher breakdown voltage as compared to the low breakdown voltage MISFET, and thus, it is necessary to secure a large interval between the source and drain regions. Accordingly, it is necessary to form a sidewall, which is adjacent to the gate electrode (for example, a control gate electrode or the like), to have a large width. That is, it is necessary to form a plurality of kinds of sidewalls having different widths on a semiconductor substrate in order to realize a sufficient breakdown voltage performance of the high breakdown voltage MISFET and to narrow the interval between the source and drain regions of the low breakdown voltage MISFET. Hereinafter, a description will be given regarding the method of manufacturing the semiconductor device according to the comparative example in which the above-described sidewalls are formed. 
     First, various gate electrodes are formed by performing the same processes as the processes that have been described with reference to  FIGS. 1 to 12 , and then, an offset spacer (not illustrated) covering sidewalls of the various gate electrodes, and the extension regions EX 2  and EX 4  of the main surface of the semiconductor substrate SB are formed as illustrated in  FIG. 62 . Subsequently, a silicon nitride film NTA and a silicon oxide film OXA are sequentially formed on the semiconductor substrate SB using a CVD method or the like. Here, a distance between the gate electrodes G 2  in the logic circuit region LN is, for example, 108 to 128 nm. In addition, a film thickness of the silicon nitride film NTA is 20 nm, and a film thickness of the silicon oxide film OXA is 26 nm. Accordingly, a gap between the gate electrode G 2  is not completely embedded by forming the silicon nitride film NTA and the silicon oxide film OXA. 
     Next, etchback is performed to form the silicon oxide film OXA in a sidewall shape and to expose the upper surface of the silicon nitride film NTA as illustrated in  FIG. 63 . Next, the memory cell region HM is covered by a photoresist film PRA, and the silicon oxide film OXA in the logic circuit region LN is removed as illustrated in  FIG. 64 . Next, the photoresist film PRA is removed, and then, etchback is selectively performed to remove the silicon nitride film NTA that is exposed from the silicon oxide film OXA so that the main surface of the semiconductor substrate SB is exposed as illustrated in  FIG. 65 . 
     Accordingly, a sidewall SWA, formed using the silicon nitride film NTA, is formed over the sidewalls of the gate electrode G 2 , and a sidewall SWB, formed using the silicon nitride film NTA and the silicon oxide film OXA, is formed over sidewalls of a pattern including the control gate electrode CG, the memory gate electrode MG, and the ONO film ON. A width of the sidewall SWA is 26 nm, which is a width of the silicon nitride film NTA, and a width of the sidewall SWB is 46 nm obtained by adding each film thickness of the silicon nitride film NTA and the silicon oxide film OXA. 
     In this manner, it is possible to form the sidewalls SWA and SWB having two kinds of different widths. Thereafter, a diffusion layer is formed by performing ion implantation using the sidewalls SWA and SWB and the like as a mask, and the low breakdown voltage MISFET including the gate electrode G 2  and the memory cell including the control gate electrode CG and the memory gate electrode MG are formed although not illustrated. 
     Due to a request for miniaturization of a semiconductor device, there is a tendency that each interval among a plurality of gate electrodes of low breakdown voltage MISFET&#39;s forming the logic circuit is reduced more than each interval among a plurality of gate electrodes of high breakdown voltage transistors to be formed in the I/O region or the memory cell region. The interval between the gate electrodes of the low breakdown voltage MISFET, for which a high degree of integration is required as above, is reduced more and more along with the miniaturization of the semiconductor device. Although the description has been given in  FIGS. 62 to 65  regarding the case in which the interval between the gate electrodes in the logic circuit region is relatively large, a description will be given regarding a problem that is caused when the interval between the gate electrodes in the logic circuit region is small, hereinafter, as a method of manufacturing a semiconductor device according to a comparative example. Here, a distance between the gate electrodes in the logic circuit region is 90 nm. 
     In this case, when the silicon nitride film NTA and the silicon oxide film OXA that cover the gate electrode G 2 , the control gate electrode CG and the memory gate electrode MG are formed by performing the process that has been described with reference to  FIG. 62 , the gate between the gate electrodes G 2  in the logic circuit region LN is completely embedded by the silicon nitride film NTA and the silicon oxide film OXA as illustrated in  FIG. 66 . That is, the silicon oxide films OXA, each of which is formed along each of opposing sidewalls of the gate electrode G 2 , are in contact with each other since a total film thickness of the silicon nitride film NTA and the silicon oxide film OXA is 46 nm, and the distance between the gate electrodes G 2  is 90 nm. 
     Next, the silicon oxide film OXA is subjected to etchback as illustrated in  FIG. 67  by performing the same process as the process that has been described with reference to  FIG. 63 . Subsequently, the memory cell region HM is covered by the photoresist film PRA. 
     Next, etching is performed using the photoresist film PRA as a mask to remove the silicon oxide film OXA in the logic circuit region LN as illustrated in  FIG. 68  by performing the same process as the process that has been described with reference to  FIG. 64 . However, it is difficult to remove the silicon oxide film OXA embedded between the gate electrodes G 2  with the etching amount at a level of removing the sidewall-shaped silicon oxide film OXA that is not embedded between the gate electrodes G 2 , and there is a risk that the silicon oxide film OXA remains between the gate electrodes G 2 . 
     In this case, it is difficult to remove the silicon nitride film NTA below the silicon oxide film OXA remaining between the gate electrodes G 2  even when the process of removing the silicon nitride film NTA that has been described with reference to  FIG. 65  is subsequently performed, and it is difficult to form a desired diffusion layer on the main surface of the semiconductor substrate SB between the gate electrodes G 2  in the subsequent ion implantation process. Accordingly, there occurs a problem that the reliability of the semiconductor device deteriorates. 
     In addition, when the etching amount is increased in order to completely remove the silicon oxide film OXA between the gate electrodes G 2 , illustrated in  FIG. 68 , by etching, the silicon nitride film NTA, covered by the silicon oxide film OXA that is not embedded between the gate electrodes G 2 , is excessively etched by the etching, and the film thickness of the silicon nitride film NTA on some of the sidewalls of the gate electrode G 2  is decreased. Accordingly, a variation is caused in widths of sidewalls, which are formed, respectively, on both sides of the gate electrode G 2 , and there occurs the problem that the reliability of the semiconductor device deteriorates. 
     In addition, when the etching amount is increased in order to completely remove the silicon oxide film OXA between the gate electrodes G 2 , illustrated in  FIG. 68 , by etching, the silicon nitride film NTA covered by the silicon oxide film OXA that is not embedded between the gate electrodes G 2  is excessively etched by the etching, and the main surface of the semiconductor substrate SB are exposed in some cases. Thereafter, when the process of removing the silicon nitride film NTA that has been described with reference to  FIG. 65  is performed, the exposed main surface of the semiconductor substrate SB is recessed, and further, the main surface is damaged. When the main surface of the semiconductor substrate SB is recessed, the punch-through between the source and drain regions is likely to occur, and there occurs a problem that the breakdown voltage of the MISFET decreases. 
     Such a problem occurs because the sidewall SWB (see  FIG. 65 ) of the high breakdown voltage MISFET is formed only using the silicon nitride film NTA and the silicon oxide film OXA which are formed in the process that has been described with reference to  FIG. 62 . Incidentally, a film thickness (width) of the offset spacer (not illustrated) is enough small to be ignorable in the above-described problem in relation to the embedment between the gate electrodes G 2 . 
     Thus, in this embodiment, the silicon nitride film NT 3  and the silicon oxide film OX 4  are formed through the process that has been described with reference to  FIG. 20 , then, the silicon oxide film OX 4  in the logic circuit region LN is removed, and the sidewall SW 2  (see  FIG. 24 ), which includes the silicon oxide film OX 5  (see  FIG. 23 ) to be formed thereafter, the silicon oxide film OX 4 , and the silicon nitride film NT 3 , is formed. Thus, the silicon oxide films OX 4  and OX 5 , and the silicon nitride film NT 3  are not simultaneously formed between the neighboring gate electrodes G 2 . That is, an insulating film having a total film thickness (a+b+c) of 46 nm is not formed at the same time in the region between the gate electrodes G 2  that has the width of 90 nm. Accordingly, it is possible to prevent the generation of the problem in the comparative example illustrated in  FIG. 68  in which it is difficult to suitably remove the insulating film between the gate electrodes G 2 . 
     That is, the sidewall SW 2  of the high breakdown voltage MISFET is not formed only using the silicon nitride film NT 3  and the silicon oxide film OX 4  (see  FIG. 20 ), which are formed first in the process of forming the sidewalls SW 1  and SW 2 , but the silicon oxide film OX 4  in the logic circuit region LN is removed after depositing the silicon nitride film NT 3  and the silicon oxide film OX 4  in this embodiment. Further, the silicon oxide film OX 5  is formed thereafter, and a required width of the sidewall SW 2  is secured by the total film thickness of the three films including the silicon oxide films OX 4  and OX 5 , and the silicon nitride film NT 3 . 
     Thus, it is unnecessary for the total film thickness of the silicon nitride film NT 3  and the silicon oxide film OX 4 , which are formed first in the process of forming the sidewalls SW 1  and SW 2 , to satisfy the required width of the sidewall SW 2 . Accordingly, it is possible to prevent the gap between the gate electrode G 2  from being embedded at the time of forming the silicon nitride film NT 3  and the silicon oxide film OX 4  first in the process of forming the sidewalls SW 1  and SW 2 . 
     Accordingly, the removal failure of the insulating film, which has been described using the comparative example of  FIG. 68 , does not occur, and thus, it is possible to form the desired diffusion layer in the logic circuit region LN in the ion implantation process that is performed after the process that has been described with reference to  FIG. 24 . In addition, it is possible to prevent the generation of the variation in width of the sidewall SW 1  beside the gate electrode G 2 . In addition, it is possible to prevent the recess of the main surface of the semiconductor substrate SB in the process of removing the silicon nitride film NT 3  (see  FIG. 24 ) that is caused when a part of the silicon nitride film NT 3  is excessively removed in the process of removing the silicon oxide film OX 4  (see  FIG. 22 ). Accordingly, it is possible to improve the reliability of the semiconductor device. 
     In addition, it is possible to secure the breakdown voltage of the high breakdown voltage MISFET and to narrow the interval between the source and drain regions of the low breakdown voltage MISFET by forming the sidewalls SW 1  and SW 2  having different widths. Thus, it is possible to realize the improvement in integration degree, the low power consumption, and the high-speed operation of the low breakdown voltage MISFET. 
     In addition, other effects of the first embodiment will be described hereinafter. 
     In this embodiment, an outer sidewall of sidewall SW 2  illustrated in  FIG. 29 , that is, the sidewall of the sidewall SW 2  at the opposite side of the sidewall on the pattern including the control gate electrode CG and the memory gate electrode MG is configured using silicon oxide. That is, the silicon oxide films OX 4  and OX 5  are formed on the outer sidewall side of the sidewall SW 2  among the sidewalls SW 2 . In addition, the silicon oxide film OX 5  is formed on an outer sidewall of the sidewall SW 1 . 
     The silicon oxide film is more easily shaved than the silicon nitride film in various processes after the process of forming the sidewall SW 2 . That is, the silicon oxide films OX 5  and OX 4  are shaved through, for example, the wet etching process of removing an unreacted metal film, which is performed after forming the silicide layer S 1  (see  FIG. 26 ), or a cleaning process. In particular, the silicon oxide films OX 5  and OX 4  damaged in the ion implantation process, which has been described with reference to  FIG. 25 , are likely to be shaved by the above-described wet etching process or the cleaning process. 
     Accordingly, each width of the sidewalls SW 1  and SW 2  decreases after the ion implantation process because the silicon oxide films OX 5  and OX 4  have been shaved. In this case, a region, which is configured to form the contact hole CH and the contact plug CP (see  FIG. 28 ), is increased on the upper surface of the source and drain regions. Accordingly, it is possible to prevent generation of connection failure in the contact plug CP, which is caused when the contact hole is not opened at the time of forming the contact hole, even in the case of reducing each interval between the gate electrodes G 2  in the logic circuit region LN and between the patterns including the control gate electrode CG and the memory gate electrode MG in the memory cell region HM. Accordingly, it is possible to miniaturize the semiconductor device. 
     In addition, it is possible to use the silicon nitride film NT 3 , which is a different type of film from the silicon oxide film OX 4 , as the etching stopper film in the etchback process of the silicon oxide film OX 4  that has been described with reference to  FIG. 21  in this embodiment, and thus, it is possible to perform the highly accurate etching. In addition, it is possible to use the silicon nitride film NT 3  as the etching stopper film in the etchback process of the silicon oxide film OX 5  that has been described with reference to  FIG. 24 , and thus, it is possible to perform the highly accurate etching. In addition, it is possible to use a part of the silicon oxide film OX 3  (see  FIG. 29 ) as the etching stopper film in the etchback process of the silicon nitride film NT 3  that has been described with reference to  FIG. 24 , and thus, it is possible to perform the highly accurate etching. 
     That is, it is possible to prevent the recess of the main surface of the semiconductor substrate SB which is caused as the main surface of the semiconductor substrate SB is exposed to etching due to the excessive etching. That is, it is possible to prevent the decrease of the breakdown voltage of the MISFET. 
     In addition, when a part of an offset spacer is configured using a silicon nitride film, which is the same material as an ONO film, for example, it is considered a case in which sidewalls of the silicon nitride film, which is in the ONO film below a memory gate electrode, is in contact with the above-described silicon nitride film forming the offset spacer. In this case, there is a possibility that hot electrons generated during a programming operation are trapped by the offset spacer, formed using the silicon nitride film, in the vicinity of an end portion of the memory gate electrode since the above-described silicon nitride film has the charge storage function. Further, there is a risk that electrons are further stored in the offset spacer while the programming operation is repeated, and a threshold voltage in the vicinity of the end portion of the memory gate electrode increases. Such an increase of the threshold voltage leads to deterioration in mutual conductance, which is a ratio of a change in drain current in relation to a change in gate voltage, and a decrease in read current. 
     With respect to this, the sidewalls of the ONO film ON below the memory gate electrode MG, which forms the memory cell MC of the MONOS memory illustrated in  FIG. 29 , is not in contact with the silicon nitride film but is in contact with the silicon oxide film OX 3  forming the offset spacer OS 1 . Accordingly, it is possible to prevent the threshold voltage of the MISFET, which forms the memory cell MC, from abnormally increasing due to the storage of the charge inside the offset spacer OS 1  during the programming operation of the memory cell MC. 
     MODIFICATION EXAMPLE 1 
     Hereinafter, a description will be given regarding a process of manufacturing a semiconductor device according to Modification Example 1 of the first embodiment with reference to  FIGS. 31 to 43 .  FIGS. 31 to 43  are cross-sectional views during the process of manufacturing the semiconductor device according to Modification Example 1.  FIGS. 31 to 37  are the cross-sectional views illustrating the logic circuit regions LP and LN, the I/O region HV, and the memory cell region HM similarly to  FIG. 1 .  FIGS. 38 to 43  are cross-sectional views illustrating the logic circuit region LN and the memory cell region HM similarly to  FIG. 20 . 
     Here, the case of forming a metal gate electrode using the gate-last process will be described. In addition, a second method of forming an offset spacer will be described here with reference to  FIGS. 34 to 37 .  FIGS. 38 to 43 , used to describe processes after forming the offset spacer, illustrate the offset spacer OS 2  actually having the stacked structure (see  FIG. 37 ) as a single film in order to facilitate understanding of the drawings. 
     In addition, each manufacturing process in the logic circuit region LP and the I/O region HV will not be described in  FIGS. 38 to 43  and only the logic circuit region LN and the memory cell region HM will be illustrated. The manufacturing process in the logic circuit region LP is performed in the same manner as in the logic circuit region LN, and the manufacturing process in the I/O region HV is performed in the same manner as in the memory cell region HM. However, p-type impurities are injected during an ion implantation process, which is performed in order to form diffusion layers forming source and drain regions, in each manufacturing process in the logic circuit region LP and the I/O region HV, which is different from the logic circuit region LN and the memory cell region HM. In addition,  FIGS. 38 to 43  illustrate cross-sectional views of the case of forming two MISFETs side by side in the logic circuit region LN. 
     Incidentally, a distance between neighboring dummy gate electrodes DG 2  in the logic circuit region LN illustrated in  FIGS. 38 to 43  is 90 nm, for example, when ignoring a film thickness of the offset spacer OS 2 . When considering the film thickness of the offset spacer OS 2 , a distance between the offset spacers OS 2 , each of which covers each of opposing sidewalls of the neighboring dummy gate electrodes DG 2 , is 90 nm. 
     First, the processes that have been described with reference to  FIGS. 1 to 3  are performed, and then, the same processes as the processes that have been described with reference to  FIGS. 4 and 5  are performed, thereby obtaining a structure, which is the same as the structure illustrated in  FIGS. 4 and 5 , as illustrated in  FIG. 31 . Next, the same processes as the processes that have been described with reference to  FIGS. 6 and 7  are performed, thereby obtaining a structure, which is the same as the structure illustrated in  FIG. 7 , as illustrated in  FIG. 32 . 
     Next, the insulating film IF 3 , the polysilicon film PS 1 , and the insulating film IF 1  in the logic circuit regions LP and LN are patterned using a photolithography technique and a dry etching method, and a dummy gate electrode DG 1 , formed using the polysilicon film PS 1  in the logic circuit region LP, and the dummy gate electrode DG 2 , formed using the polysilicon film PS 1  in the logic circuit region LN, are formed as illustrated in  FIG. 33 . The dummy gate electrodes DG 1  and DG 2  are pseudo gate electrodes which will be removed and replaced with metal gate electrodes in the subsequent process. 
     Next, the same processes as the processes that have been described with reference to  FIGS. 13 and 14  are performed, and subsequently, the photoresist film PR 2  is removed. Thereafter, a silicon nitride film NT 4  is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 34 . A film thickness of the silicon nitride film NT 4  is, for example, 5 nm. 
     Next, the same process as the process that has been described with reference to  FIG. 16  is performed, and then, a silicon nitride film NT 5  is formed on the silicon nitride film NT 4  using, for example, a CVD method as illustrated in  FIG. 35 . That is, the main surface of the semiconductor substrate SB is covered by the silicon nitride films NT 4  and NT 5  which are sequentially formed on the main surface of the semiconductor substrate SB. A film thickness of the silicon nitride film NT 5  is, for example, 5 nm. 
     Next, etchback is performed to remove apart of a stacked film, which is formed of the silicon nitride films NT 4  and NT 5 , so that each upper surface of the main surface of the semiconductor substrate SB and the insulating film IF 3  is exposed as illustrated in  FIG. 36 . Accordingly, the stacked films, each of which remains in a sidewall-shaped over each sidewall of the dummy gate electrodes DG 1  and DG 2 , the gate electrode G 3 , and the pattern including the control gate electrode CG and the memory gate electrode MG, form the offset spacer OS 2 . 
     Next, the same processes as the processes that have been described with reference to  FIGS. 18 and 19  are performed, thereby forming the extension region EX 1  as illustrated in  FIG. 37 . 
     Next, the same processes as the processes that have been described with reference to  FIGS. 20 to 26  are performed, thereby forming source source and drain regions as illustrated in  FIG. 38 . Meanwhile, the MISFET is not yet formed since the pseudo dummy gate electrodes DG 1  (not illustrated) and DG 2  are formed in the logic circuit regions LP and LN. Subsequently, the interlayer insulating film IL 2 , the silicide layer S 1 , and the insulating film IF 3  are polished using, for example, a CMP method so that each upper surface of the dummy gate electrodes DG 1  and DG 2 , the control gate electrode CG, and the memory gate electrode MG is exposed. 
     Next, an insulating film (not illustrated) is formed so as to protect the gate electrode G 3  (not illustrated) in the I/O region HV, and each upper surface of the control gate electrode CG and the memory gate electrode MG in the memory cell region HM, and then, the dummy gate electrodes DG 1  (not illustrated) and DG 2 , and the insulating film IF 1  are removed by performing, for example, wet etching as illustrated in  FIG. 39 . A trench is formed in each of regions from which the dummy gate electrodes DG 1  and DG 2  are removed. Here, the case of removing the insulating film IF 1  has been described, but the insulating film IF 1  may be left. 
     Next, the insulating film HK is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method, and then, the metal film MF is formed by, for example, sputtering as illustrated in  FIG. 40 . The insulating film HK and the metal film MF are made of, for example, the same material as the material that has been described with reference to  FIG. 11 . The above-described trench is completely embedded by the insulating film HK and the metal film MF through this deposition process. 
     Next, the insulating film HK and the metal film MF remaining on the interlayer insulating film IL 2  are removed using, for example, a CMP method so that the upper surface of the interlayer insulating film IL 2  is exposed as illustrated in  FIG. 41 . Accordingly, the gate insulating film GF 2 , formed using the insulating film HK remaining inside the above-described trench, is formed, and the gate electrode G 2  is formed as the metal gate electrode formed using the metal film MF remaining inside the above-described trench. Subsequently, an insulating film IF 5  which is made of, for example, a silicon oxide film or the like is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method. Thereafter, the insulating film IF 5  in the I/O region HV (not illustrated) and the memory cell region HM are removed using a photolithography technique and a dry etching method. At this time, the upper surface of the gate electrode G 2  is covered by the insulating film IF 5 . 
     Next, a silicide layer S 2  is formed on each upper surface of the control gate electrode CG and the memory gate electrode MG using a known salicide process as illustrated in  FIG. 42 . The method of forming the silicide layer S 2  is the same as the method that has been described with reference to  FIG. 26 . A process of removing the unreacted metal film by wet etching is performed during the salicide process. At this time, the gate electrodes G 1  (not illustrated) and G 2  are protected by the insulating film IF 5 , and thus, are not removed. 
     Next, an interlayer insulating film IL 3  which is made of, for example, a silicon oxide film is formed on the interlayer insulating film IL 2  using, for example, a CVD method as illustrated in  FIG. 43 . Thereafter, an upper surface of the interlayer insulating film IL 3  is planarized using a CMP method or the like. Subsequently, the same processes as the processes that have been described with reference to  FIGS. 27 and 28  are performed so as to form the plurality of contact holes CH, which penetrate the interlayer insulating films IL 2  and IL 3 , and the contact plugs CP that are embedded in the contact holes CH. As above, the semiconductor device according to Modification Example 1 is completed. When the metal gate is formed using the gate-last process, it is possible to omit the processes that have been described with reference to  FIGS. 8 to 12 , and it is possible to simplify the process of manufacturing the semiconductor device. 
     Here, the MISFET Q 2  in the logic circuit region LN and the memory cell MC in the memory cell region HM are illustrated in  FIG. 44  in an enlarged manner. That is,  FIG. 44  is a cross-sectional view illustrating a part of  FIG. 43  in an enlarged manner.  FIG. 44  illustrates the stacked structure of the ONO film ON and the stacked structure of the offset spacer OS 2  in detail. In addition,  FIG. 44  does not illustrate the silicide layers S 1  and S 2 , the interlayer insulating films IL 2  and IL 3 , the contact hole CH, and the contact plug CP. As illustrated in  FIG. 44 , the silicon nitride film NT 4  forming the offset spacer OS 2  is in contact with sidewalls of the silicon nitride film NT 1  forming the ONO film ON. 
     Hereinafter, effects of Modification Example 1 will be described. The process of forming the sidewalls SW 1  and SW 2  according to the first embodiment, which has been described with reference to  FIGS. 20 to 24 , is performed in Modification Example 1. Thus, a gap between the neighboring gate electrodes G 2  is not completely embedded by the insulating film configured for formation of the sidewall SW 1  during the process of forming the sidewalls SW 1  and SW 2 . 
     Thus, it is possible to form a desired diffusion layer in the logic circuit region LN. In addition, it is possible to prevent generation of variation in width of the sidewall SW 1  beside the gate electrode G 2 . In addition, it is possible to prevent the recess of the main surface of the semiconductor substrate SB in the process of removing the silicon nitride film NT 3  (see  FIG. 24 ) that is caused when a part of the silicon nitride film NT 3  is excessively removed in the process of removing the silicon oxide film OX 4  (see  FIG. 22 ). Accordingly, it is possible to improve the reliability of the semiconductor device. In addition, it is possible to secure the breakdown voltage of the high breakdown voltage MISFET and to narrow the interval between the source and drain regions of the low breakdown voltage MISFET by forming the sidewalls SW 1  and SW 2  having different widths. Thus, it is possible to realize the improvement in integration degree, the low power consumption, and the high-speed operation of the low breakdown voltage MISFET. 
     In addition, here, an outer sidewall of sidewall SW 1  illustrated in  FIG. 44  is configured using the silicon oxide film OX 5 , and an outer sidewall of the sidewall SW 2  is configured using the silicon oxide films OX 5  and OX 4 . 
     Accordingly, the silicon oxide films OX 5  and OX 4  are shaved after the ion implantation process, and thus, each width of the sidewalls SW 1  and SW 2  decreases. In this case, a region to form the contact hole CH and the contact plug CP (see  FIG. 28 ) on the source and drain regions increases. Accordingly, it is possible to prevent the generation of connection failure in the contact plug CP, which is caused when the contact hole is not opened at the time of forming the contact hole, even in the case of reducing each interval between the gate electrodes G 2  in the logic circuit region LN and between the patterns including the control gate electrode CG and the memory gate electrode MG in the memory cell region HM. Accordingly, it is possible to miniaturize the semiconductor device. 
     In addition,  FIG. 45  illustrates a cross-sectional view of the semiconductor device according to Modification Example 1 in a case in which the MONOS memory is not formed. That is, the processes that have been described with reference to  FIGS. 30 to 37  are performed without providing the memory cell region HM in this case.  FIG. 45  illustrate the MISFET Q 2  in the logic circuit region LN and a high breakdown voltage MISFET Q 3  which is formed by performing the process that has been performed with respect to the memory cell region HM in the processes described with reference to  FIG. 31  to  FIG. 43 , with respect to the I/O region HV. 
     As illustrated in  FIG. 45 , the MISFET Q 3  in the I/O region HV includes the extension region EX 3  and a diffusion layer DF 3 , which are n-type semiconductor regions, and the gate electrode G 3  on the gate insulating film GF 3 . In addition, the sidewall SW 2  is formed over sidewalls of the gate electrode G 3  with the offset spacer OS 2  interposed therebetween, which is similar to the film covering sidewalls of the pattern including the control gate electrode CG and the memory gate electrode MG illustrated in  FIG. 44 . 
     Since the MONOS memory cell is not present in the structure illustrated in  FIG. 45 , the silicon nitride film, which forms the ONO film as the charge storage film, is not in contact with the silicon nitride film NT 4  forming the offset spacer OS 2 . Thus, there is no case in which charge is stored in the offset spacer OS 2  during the programming operation of the semiconductor device. That is, Modification Example 1 in which the offset spacer OS 2  is formed only of the silicon nitride films NT 4  and NT 5  is advantageous in terms that it is possible to prevent the malfunction of the semiconductor device when being applied to the semiconductor device in which the MONOS memory cell is not formed. 
     Incidentally, the method of forming the insulating film HK (see  FIG. 40 ), which is a high-k film, after removing the dummy gate electrode during the gate-last process in which the dummy gate electrode is replaced with the metal gate electrode is used in Modification Example 1. However, the insulating film HK may be formed in the logic circuit region before forming the polysilicon film PS 1  (see  FIG. 31 ), which forms the dummy gate electrode, and the insulating film HK may be left as each part of the gate insulating films GF 1  (not illustrated) and GF 2  illustrated in  FIG. 43 . In this case, for example, it is considered a method of forming the insulating film HK on the main surface of the semiconductor substrate SB after performing the process that has been described with reference to  FIG. 2 , and subsequently, removing the insulating film HK in a region other than the logic circuit regions LP and LN. This is similarly applied in the following Modification Example 2 and a second embodiment and Modification Example 1 of the second embodiment to be described later. 
     MODIFICATION EXAMPLE 2 
     Hereinafter, a description will be given regarding a process of manufacturing a semiconductor device according to Modification Example 2 of the first embodiment with reference to  FIGS. 46 to 51 .  FIGS. 46 to 51  are cross-sectional views during the process of manufacturing the semiconductor device according to Modification Example 2.  FIGS. 46 to 50  are the cross-sectional view illustrating the logic circuit regions LP and LN, the I/O region HV, and the memory cell region HM similarly to  FIG. 1 .  FIG. 51  is the cross-sectional view illustrating the logic circuit region LN and the memory cell region HM similarly to  FIG. 20 . 
     Here, the case of forming a metal gate electrode using the gate-last process will be described. In addition, a third method of forming an offset spacer will be described here with reference to  FIGS. 46 to 50 .  FIG. 51 , used to describe processes after forming the offset spacer, illustrates each of offset spacers OS 3  and OS 4  actually having a stacked structure (see  FIG. 50 ) as a single film in order to facilitate understanding of the drawings. 
     In addition, each manufacturing process in the logic circuit region LP and the I/O region HV will not be described in  FIG. 51  and only the logic circuit region LN and the memory cell region HM will be illustrated. The manufacturing process in the logic circuit region LP is performed in the same manner as in the logic circuit region LN, and the manufacturing process in the I/O region HV is performed in the same manner as in the memory cell region HM. However, p-type impurities are injected during an ion implantation process, which is performed in order to form diffusion layers forming source and drain regions, in each manufacturing process in the logic circuit region LP and the I/O region HV, which is different from the logic circuit region LN and the memory cell region HM. In addition,  FIG. 51  illustrates the cross-sectional view of the case of forming two MISFETs side by side in the logic circuit region LN. 
     Incidentally, a distance between the neighboring gate electrodes G 2  in the logic circuit region LN illustrated in  FIG. 51  is 90 nm, for example, when ignoring a film thickness of the offset spacer OS 3 . When considering the film thickness of the offset spacer OS 3 , a distance between the offset spacers OS 3 , each of which covers each of opposing sidewalls of the neighboring gate electrodes G 2 , is 90 nm. 
     First, the processes that have been described with reference to  FIGS. 1 to 3 and 31 to 33  are performed, and then, the same processes as the processes that have been described with reference to  FIGS. 13 and 14  are performed. Subsequently, a sidewall-shaped silicon oxide film OX 6  is formed over each sidewall of the dummy gate electrodes DG 1  and DG 2 , the gate electrode G 3 , and the pattern including the control gate electrode CG and the memory gate electrode MG as illustrated in  FIG. 46 . That is, the silicon oxide film OX 6  is formed on the semiconductor substrate SB using, for example, a CVD method, and then, etchback is performed to remove a part of the silicon oxide film OX 6  so that each upper surface of the main surface of the semiconductor substrate SB and the insulating film IF 3  is exposed. The silicon oxide film OX 6  is processed in the sidewall shape through this process. A film thickness of the silicon oxide film OX 6  is, for example, 5 nm. 
     Next, a photoresist film PR 6  is formed to cover the I/O region HV and the memory cell region HM, and wet etching is performed to remove the silicon oxide film OX 6  exposed from the photoresist film PR 6  in the logic circuit regions LP and LN as illustrated in  FIG. 47 . 
     Next, the photoresist film PR 6  is removed, and then, a silicon nitride film NT 6  is formed on the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 48 . Accordingly, the main surface of the semiconductor substrate SB, the dummy gate electrodes DG 1  and DG 2 , the gate electrode G 3 , and the pattern including the control gate electrode CG and the memory gate electrode MG are covered by the silicon nitride film NT 6 . A film thickness of the silicon nitride film NT 6  is, for example, 5 nm. 
     Next, the process of forming the extension region EX 2  which has been described with reference to  FIG. 16  is performed, and then, the photoresist film PR 3  (see  FIG. 16 ) is removed. Subsequently, a silicon nitride film NT 7  is formed on the semiconductor substrate SB using, for example, a CVD method as illustrated in  FIG. 49 . Accordingly, the silicon nitride film NT 6  is covered by the silicon nitride film NT 7 . A film thickness of the silicon nitride film NT 7  is, for example, 5 nm. 
     Next, a stacked film formed of the silicon nitride films NT 6  and NT 7  is subjected to etchback so that each upper surface of the main surface of the semiconductor substrate SB and the insulating film IF 3  is exposed as illustrated in  FIG. 50 . Accordingly, the offset spacer OS 3  formed using the stacked film and the offset spacer OS 4  including the stacked film and the silicon oxide film OX 6  are formed. 
     That is, the offset spacer OS 3  formed of the silicon nitride films NT 6  and NT 7  is formed over each sidewall of the dummy gate electrodes DG 1  and DG 2  in the logic circuit regions LP and LN. In addition, the offset spacer OS 4  formed of the silicon oxide film OX 6  and the silicon nitride films NT 6  and NT 7  is formed over each sidewall of the gate electrode G 3  and each sidewall of the pattern, which includes the control gate electrode CG and the memory gate electrode MG in the I/O region HV and the memory cell region HM. The offset spacer OS 3  does not include the silicon oxide film OX 6 , and thus, has a smaller width than the offset spacer OS 4 . 
     Subsequently, the process of forming the extension region EX 1  that has been described with reference to  FIG. 18  is performed, and then, the photoresist film PR 4  (see  FIG. 18 ) is removed as described with reference to  FIG. 19 . Accordingly, the structure illustrated in  FIG. 50  is obtained. 
     Next, the semiconductor device according to Modification Example 2 is completed as illustrated in  FIG. 51  by performing the same processes as the processes that have been described with reference to  FIGS. 20 to 26 and 38 to 43 . That is, the dummy gate electrodes DG 1  and DG 2  is replaced with the metal gate electrode through the gate-last process, and the MISFET Q 2  including the metal gate electrode and the memory cell MC including the high breakdown voltage MISFET are formed. 
     Here,  FIG. 52  illustrates the MISFET Q 2  and the memory cell MC of  FIG. 51  in an enlarged manner. That is,  FIG. 52  is the cross-sectional view illustrating a part of  FIG. 51  in an enlarged manner.  FIG. 52  illustrates the stacked structure of the ONO film ON and each stacked structure of the offset spacers OS 3  and OS 4  in detail. In addition,  FIG. 52  does not illustrate the silicide layers S 1  and S 2 , the interlayer insulating films IL 2  and IL 3 , the contact hole CH, and the contact plug CP. 
     As illustrated in  FIG. 52 , the sidewalls of the silicon nitride film NT 1  forming the ONO film ON is in contact with the silicon oxide film OX 6  forming the offset spacer OS 4 , and is not in contact with the silicon nitride film. In addition, the offset spacer OS 4  and the sidewall SW 2  are sequentially formed over the sidewall of the patterns including the control gate electrode CG, the ONO film ON, and the memory gate electrode MG. In other words, the sidewall SW 2  is formed over the sidewall of the pattern with the offset spacer OS 4  interposed therebetween. 
     In Modification Example 2, it is possible to obtain the same effects as Modification Example 1 that has been described with reference to  FIGS. 31 to 44 . In addition, it is possible to obtain another effect as the silicon nitride film is not in contact with the ONO film. That is, it is possible to prevent the threshold voltage of the MISFET, which forms the memory cell MC, from abnormally increasing due to the storage of the charge inside the offset spacer OS 4  in the vicinity of the ONO film ON during the programming operation of the memory cell MC since the sidewall of the silicon nitride film NT 1  forming the ONO film ON is in contact only with the silicon oxide film OX 6  covering the sidewall. 
     Second Embodiment 
     Hereinafter, a description will be given regarding a method of manufacturing a semiconductor device according to the second embodiment with reference to  FIGS. 53 to 55 . Here, a description will be given regarding the case of forming an outer portion as a part of a sidewall using a silicon nitride film when the second method, which has been described with reference to  FIGS. 34 to 37 , is used to form the offset spacer.  FIGS. 53 to 55  illustrate the offset spacer OS 2  as a single film in order to facilitate understanding of the drawings. The main difference of the second embodiment from Modification Example 1 of the first embodiment is that the silicon nitride film is formed instead of the silicon oxide film OX 5  (see  FIG. 23 ). 
     Each manufacturing process in the logic circuit region LP and the I/O region HV will not be described in  FIGS. 53 to 55  and only the logic circuit region LN and the memory cell region HM will be illustrated. The manufacturing process in the logic circuit region LP is performed in the same manner as in the logic circuit region LN, and the manufacturing process in the I/O region HV is performed in the same manner as in the memory cell region HM. However, p-type impurities are injected during an ion implantation process, which is performed in order to form diffusion layers forming source and drain regions, in each manufacturing process in the logic circuit region LP and the I/O region HV, which is different from the logic circuit region LN and the memory cell region HM. In addition,  FIGS. 53 to 55  illustrate the cross-sectional views of the case of forming two MISFETs side by side in the logic circuit region LN. 
     Incidentally, a distance between the neighboring dummy gate electrodes DG 2  in the logic circuit region LN is 90 nm, for example, when ignoring a film thickness of the offset spacer OS 2 . When considering the film thickness of the offset spacer OS 2 , a distance between the offset spacers OS 2 , each of which covers each of opposing sidewalls of the neighboring dummy gate electrodes DG 2 , is 90 nm. 
     In the second embodiment, first, the same process as the processes as the processes that have been described with reference to  FIGS. 1 to 3 and 31 to 37  are performed, thereby forming the dummy gate electrodes DG 1  and DG 2 , the gate electrode G 3 , the control gate electrode CG, the memory gate electrode MG, and the offset spacer OS 2  as illustrated in  FIG. 53 . Thereafter, the same processes as the processes that have been described with reference to  FIGS. 20 to 22  are performed, thereby forming the silicon nitride film NT 3  and the sidewall-shaped silicon oxide film OX 4 . Thereafter, the photoresist film PR 5  (see  FIG. 22 ) is removed, and then, a silicon nitride film NT 8  is formed on the main surface of the semiconductor substrate SB using, for example, a CVD method. Accordingly, the silicon nitride film NT 3  and the silicon oxide film OX 4  are covered by the silicon nitride film NT 8 . 
     Here, a film thickness a of the silicon nitride film NT 3  is, for example, 10 nm, a film thickness b of the silicon oxide film OX 4  is, for example, 20 nm, and a film thickness c of the silicon nitride film NT 8  is, for example, 16 nm. Accordingly, silicon nitride film NT 3  and the silicon oxide film OX 4  are formed in the process that has been described with reference to  FIG. 20 , a region having a width of 90 nm between the neighboring dummy gate electrodes DG 2  is not completely embedded since a total film thickness of the silicon nitride film NT 3  and the silicon oxide film OX 4  is 30 nm. 
     Next, etchback is performed to remove each part of the silicon nitride films NT 8  and NT 3  as illustrated in  FIG. 54 . Accordingly, the main surface of the semiconductor substrate SB and the upper surface of the insulating film IF 3  are exposed. Through this etchback, a sidewall SW 3 , which is formed of the silicon nitride films NT 3  and NT 8  and covers the sidewall of the dummy gate electrode DG 2 , is formed in the logic circuit region LN. In addition, a sidewall SW 4 , which is formed of the silicon nitride film NT 3 , the silicon oxide film OX 4 , and the silicon nitride film NT 8 , and covers the sidewall of the pattern including the control gate electrode CG, the ONO film ON, and the memory gate electrode MG, is formed in the memory cell region HM through the etchback. 
     A width of the sidewall SW 3  has the same dimension as a total film thickness of the silicon nitride films NT 3  and NT 8 , that is, 26 nm. A width of the sidewall SW 4  has the same dimension as a total film thickness of the silicon nitride film NT 3 , the silicon oxide film OX 4 , and the silicon nitride film NT 8  that is, 46 nm. In this manner, it is possible to form the sidewalls SW 3  and SW 4  having two kinds of different widths. 
     Next, the semiconductor device according to the second embodiment is completed by performing the processes that have been described with reference to  FIGS. 25, 26 and 38 to 43  as illustrated in  FIG. 55 . In the second embodiment, it is possible to prevent the gap between the dummy gate electrodes DG 2  from being completely embedded at the time of forming the silicon nitride film NT 3  and the silicon oxide film OX 4  by performing the same process as the process that has been described with reference to  FIG. 22 . Accordingly, the removal failure of the insulating film, which has been described using the comparative example in  FIG. 68 , does not occur, and thus, it is possible to form a desired diffusion layer in the logic circuit region LN in an ion implantation process which is performed after the process that has been described with reference to  FIG. 54 . 
     In addition, it is possible to prevent generation of variation in width of the sidewall SW 3  beside the gate electrode G 2 . In addition, it is possible to prevent the recess of the main surface of the semiconductor substrate SB in the process of removing the silicon nitride film NT 3  (see  FIG. 54 ) that is caused when a part of the silicon nitride film NT 3  is excessively removed in the process of removing the silicon oxide film OX 4  (see  FIG. 22 ). Accordingly, it is possible to improve the reliability of the semiconductor device. 
     In addition, it is possible to secure the breakdown voltage of the high breakdown voltage MISFET and to narrow the interval between the source and drain regions of the low breakdown voltage MISFET by forming the sidewalls SW 3  and SW 4  having different widths. Thus, it is possible to realize the improvement in integration degree, the low power consumption, and the high-speed operation of the low breakdown voltage MISFET. 
     Here,  FIG. 56  illustrates a cross-sectional view of the MISFET Q 2  and the memory cell MC formed through the above-described manufacturing process in an enlarged manner. That is,  FIG. 56  is the cross-sectional view illustrating a part of  FIG. 55  in an enlarged manner.  FIG. 56  illustrates the stacked structure of the ONO film ON and the stacked structure of the offset spacer OS 2  in detail. In addition,  FIG. 56  does not illustrate the silicide layers S 1  and S 2 , the interlayer insulating films IL 2  and IL 3 , and the contact plug CP. As illustrated in  FIG. 56 , the sidewall SW 3 , formed of the silicon nitride films NT 3  and NT 8 , is formed over sidewalls of the stacked film including the insulating film HK and the metal film MF with the offset spacer OS 2 , formed of the silicon nitride films NT 4  and NT 5 , interposed therebetween in the logic circuit region LN. 
     For example, when a gate insulating film of a MISFET of a low breakdown voltage formed in a logic circuit region includes a high-k film, or, when the gate electrode of the MISFET is a metal gate electrode, the following problem occurs. That is, when an offset spacer or a sidewall including a silicon oxide film is formed in the vicinity of the high-k film or the metal gate electrode, oxygen inside the silicon oxide film moves to the high-k film or the metal gate electrode and cause reaction with a material of the high-k film or the metal gate electrode. Accordingly, properties of the MISFET are changed, and there occurs a problem that the reliability of the element deteriorates. 
     With respect to this, the offset spacer OS 2 , which is adjacent to the insulating film HK serving as the high-k film and the metal film MF forming the metal gate electrode, is formed only of the silicon nitride films NT 4  and NT 5  in the second embodiment as illustrated in  FIG. 56 . In addition, the sidewall SW 3 , which covers the sidewall of the stacked film formed of the insulating film HK and the metal film MF, is formed only of the silicon nitride films NT 3  and NT 8 . That is, the offset spacer OS 2  and the sidewall SW 3  do not include the silicon oxide film. Thus, it is possible to prevent oxygen from intruding into the insulating film HK and the metal film MF from the offset spacer OS 2  and the sidewall SW 3 , and thus, it is possible to prevent the change in properties of the element due to the reaction between the oxygen and the insulating film HK or the metal film MF. Accordingly, it is possible to improve the reliability of the semiconductor device. 
     In addition,  FIG. 57  illustrates a cross-sectional view of the semiconductor device according to the second embodiment in a case in which a MONOS memory is not formed. That is, the processes that have been described with reference to  FIGS. 53 to 55  are performed without providing the memory cell region HM in this case.  FIG. 57  illustrates the MISFET Q 2  in the logic circuit region LN and the high breakdown voltage MISFET Q 3  which is formed by performing the process that has been performed with respect to the memory cell region HM in the processes described with reference to  FIGS. 53 to 55 , with respect to the I/O region HV. The sidewall SW 4  is formed over sidewalls of the gate electrode G 3  illustrated in  FIG. 57  with the offset spacer OS 2  interposed therebetween similarly to a film covering sidewalls of the pattern, which includes the control gate electrode CG and the memory gate electrode MG, illustrated in  FIG. 56 . 
     In this case, similarly to the structure that has been described with reference to  FIG. 45 , it is obtained the advantage that it is possible to prevent the malfunction of the semiconductor device, which is caused when the offset spacer OS 2  formed only of the silicon nitride films NT 4  and NT 5  is formed, since the MONOS memory cell is not present. 
     MODIFICATION EXAMPLE 1 
     Hereinafter, a description will be given regarding a process of manufacturing a semiconductor device according to Modification Example 1 of the second embodiment with reference to  FIG. 58 .  FIG. 58  is a cross-sectional view during the process of manufacturing the semiconductor device according to Modification Example 1.  FIG. 58  is the cross-sectional view illustrating the logic circuit region LN and the memory cell region HM similarly to  FIG. 20 . 
     Here, the case of forming a metal gate electrode using the gate-last process will be described. In addition, the description will be given here regarding the case of combining the above-described third method of forming the offset spacer that has been described with reference to  FIGS. 46 to 50  and the method of forming the sidewall whose outer portion is made of the silicon nitride film which has been described with reference to  FIGS. 53 and 54 .  FIG. 58 , used to describe processes after forming the offset spacer, illustrates each of the offset spacers OS 3  and OS 4  actually having a stacked structure (see  FIG. 50 ) as a single film in order to facilitate understanding of the drawings. 
     In addition, each manufacturing process in the logic circuit region LP and the I/O region HV (see  FIG. 1 ) will not be described in  FIG. 51  and only the logic circuit region LN and the memory cell region HM will be illustrated. 
     In Modification Example 1, the same processes as the processes that have been described with reference to  FIGS. 1 to 3 and 31 to 33  are performed, thereby forming various gate electrodes as illustrated in  FIG. 58 . Then, the same processes as the processes that have been described with reference to  FIGS. 46 to 50  are performed, thereby forming the offset spacers OS 3  and OS 4 . Thereafter, the semiconductor device according to Modification Example 1 is completed by performing the same processes as the processes that have been described with reference to  FIGS. 20 to 22  and then the same processes as the processes that have been described with reference to  FIGS. 53 to 55 . 
     In Modification Example 1, it is possible to prevent the gap between the dummy gate electrodes DG 2  from being completely embedded at the time of forming the silicon nitride film NT 3  and the silicon oxide film OX 4  by performing the same process as the process that has been described with reference to  FIG. 22 . Accordingly, the removal failure of the insulating film, which has been described using the comparative example in  FIG. 68 , does not occur, and thus, it is possible to form a desired diffusion layer in the logic circuit region LN in an ion implantation process which is performed after the process that has been described with reference to  FIG. 54 . 
     In addition, it is possible to prevent generation of variation in width of the sidewall SW 3  beside the gate electrode G 2 . In addition, it is possible to prevent the recess of the main surface of the semiconductor substrate SB in the process of removing the silicon nitride film NT 3  (see  FIG. 54 ) that is caused when a part of the silicon nitride film NT 3  is excessively removed in the process of removing the silicon oxide film OX 4  (see  FIG. 22 ). Accordingly, it is possible to improve the reliability of the semiconductor device. 
     In addition, it is possible to secure the breakdown voltage of the high breakdown voltage MISFET and to narrow the interval between the source and drain regions of the low breakdown voltage MISFET by forming the sidewalls SW 3  and SW 4  having different widths. Thus, it is possible to realize the improvement in integration degree, the low power consumption, and the high-speed operation of the low breakdown voltage MISFET. 
     Here,  FIG. 59  illustrates a cross-sectional view of the MISFET Q 2  and the memory cell MC formed through the above-described manufacturing process in an enlarged manner. That is,  FIG. 59  is the cross-sectional view illustrating a part of  FIG. 58  in an enlarged manner.  FIG. 59  illustrates the stacked structure of the ONO film ON and each stacked structure of the offset spacers OS 3  and OS 4  in detail. In addition,  FIG. 59  does not illustrate the silicide layers S 1  and S 2 , the interlayer insulating films IL 2  and IL 3 , and the contact plug CP. As illustrated in  FIG. 59 , the sidewall SW 3 , formed of the silicon nitride films NT 3  and NT 8 , is formed over sidewalls of the stacked film including the insulating film HK and the metal film MF with the offset spacer OS 3 , formed of the silicon nitride films NT 6  and NT 7 , interposed therebetween in the logic circuit region LN. 
     That is, the offset spacer OS 3 , which is adjacent to the insulating film HK serving as the high-k film and the metal film MF forming the metal gate electrode, is formed only of the silicon nitride films NT 6  and NT 7 . In addition, the sidewall SW 3 , which covers the sidewall of the stacked film formed of the insulating film HK and the metal film MF, is formed only of the silicon nitride films NT 3  and NT 8 . That is, the offset spacer OS 3  and the sidewall SW 3  do not include the silicon oxide film. Thus, it is possible to prevent oxygen from intruding into the insulating film HK and the metal film MF from the offset spacer OS 3  and the sidewall SW 3 , and thus, it is possible to prevent the change in properties of the element due to the reaction between the oxygen and the insulating film HK or the metal film MF. Accordingly, it is possible to improve the reliability of the semiconductor device. 
     In addition, the sidewalls of the silicon nitride film NT 1  forming the ONO film ON is in contact with the silicon oxide film OX 6  forming the offset spacer OS 4  and is not in contact with the silicon nitride film as illustrated in  FIG. 59 . Accordingly, it is possible to obtain the effect which is obtained when the silicon nitride film is not in contact with the ONO film. That is, it is possible to prevent the threshold voltage of the MISFET, which forms the memory cell MC, from abnormally increasing due to the storage of the charge inside the offset spacer OS 4  in the vicinity of the ONO film ON during the programming operation of the memory cell MC since the sidewall of the silicon nitride film NT 1  forming the ONO film ON is in contact only with the silicon oxide film OX 6  covering the sidewall. 
     MODIFICATION EXAMPLE 2 
     Hereinafter, a description will be given regarding a process of manufacturing a semiconductor device according to Modification Example 2 of the second embodiment with reference to  FIG. 60 .  FIG. 60  is a cross-sectional view during the process of manufacturing the semiconductor device according to Modification Example 2.  FIG. 60  is the cross-sectional view illustrating the logic circuit region LN and the memory cell region HM similarly to  FIG. 20 . 
     Here, the case of forming a metal gate electrode using the gate-first process will be described. In addition, the description will be given here regarding the case of combining the above-described first method of forming the offset spacer that has been described with reference to  FIGS. 13 to 19  and the method of forming the sidewall whose outer portion is made of the silicon nitride film which has been described with reference to  FIGS. 53 and 54 . 
       FIG. 60 , used to describe processes after forming the offset spacer, illustrates the offset spacer OS 1  actually having a stacked structure (see  FIG. 19 ) as a single film in order to facilitate understanding of the drawings. In addition, each manufacturing process in the logic circuit region LP and the I/O region HV will not be described in  FIG. 60  and only the logic circuit region LN and the memory cell region HM will be illustrated. 
     In Modification Example 2, various gate electrodes and the offset spacer OS 1  are formed by performing the same processes as the processes that have been described with reference to  FIGS. 1 to 19 , and the sidewalls SW 3  and SW 4  are formed by performing the same processes as the processes that have been described with reference to  FIGS. 20 to 22, 53 and 54  as illustrated in  FIG. 60 . Subsequently, the semiconductor device according to Modification Example 2 illustrated in  FIG. 60  is completed by performing the processes that have been described with reference to  FIGS. 25 to 28 . 
     In Modification Example 2, it is possible to prevent the gap between the dummy gate electrodes DG 2  from being completely embedded at the time of forming the silicon nitride film NT 3  and the silicon oxide film OX 4  by performing the same process as the process that has been described with reference to  FIG. 22 . Accordingly, the removal failure of the insulating film, which has been described using the comparative example in  FIG. 68 , does not occur, and thus, it is possible to form a desired diffusion layer in the logic circuit region LN in an ion implantation process which is performed after the process that has been described with reference to  FIG. 54 . 
     In addition, it is possible to prevent generation of variation in width of the sidewall SW 3  beside the gate electrode G 2 . In addition, it is possible to prevent the recess of the main surface of the semiconductor substrate SB in the process of removing the silicon nitride film NT 3  (see  FIG. 54 ) that is caused when a part of the silicon nitride film NT 3  is excessively removed in the process of removing the silicon oxide film OX 4  (see  FIG. 22 ). Accordingly, it is possible to improve the reliability of the semiconductor device. 
     In addition, it is possible to secure the breakdown voltage of the high breakdown voltage MISFET and to narrow the interval between the source and drain regions of the low breakdown voltage MISFET by forming the sidewalls SW 3  and SW 4  having different widths. Thus, it is possible to realize the improvement in integration degree, the low power consumption, and the high-speed operation of the low breakdown voltage MISFET. 
     Here,  FIG. 61  illustrates a cross-sectional view of the MISFET Q 2  and the memory cell MC formed through the above-described manufacturing process in an enlarged manner. That is,  FIG. 61  is the cross-sectional view illustrating a part of  FIG. 60  in an enlarged manner.  FIG. 61  illustrates the stacked structure of the ONO film ON and the stacked structure of the offset spacer OS 1  in detail. In addition,  FIG. 61  does not illustrate the silicide layer S 1 , the interlayer insulating film IL 2 , and the contact plug CP. 
     Here, it is possible to obtain the effect that is obtained when the silicon nitride film is not in contact with the ONO film. That is, it is possible to prevent the threshold voltage of the MISFET, which forms the memory cell MC, from abnormally increasing due to the storage of the charge inside the offset spacer OS 1  in the vicinity of the ONO film ON during the programming operation of the memory cell MC since the sidewall of the silicon nitride film NT 1  forming the ONO film ON is in contact only with the silicon oxide film OX 3  covering the sidewall. 
     In addition, it is possible to use a part of the silicon oxide film OX 3  (see  FIG. 61 ), whose film type is different from the silicon nitride film NT 3 , as the etching stopper film in the etchback process of the silicon nitride film NT 3  that has been described with reference to  FIG. 54 , and thus, it is possible to perform the highly accurate etching. 
     In the foregoing, the invention made by the present inventor has been concretely described based on the embodiments. However, it is needless to say that the present invention is not limited to the foregoing embodiments and various modifications and alterations can be made within the scope of the present invention. 
     Although the description has been given regarding the case of forming the gate insulating film including the high-k film and the metal gate in the logic circuit region in the first and second embodiments, for example, the gate insulating film does not necessarily include the high-k film and the gate electrode may be formed only using polysilicon. In this case, however, it is difficult to obtain the effect of preventing the intrusion of oxygen into the high-k film and the metal gate electrode in the structure that has been described with reference to  FIG. 56  in the second embodiment. 
     It is possible to form the gate insulating film that does not include the high-k film and the polysilicon gate electrode using the method of forming the dummy gate electrode that has been described with reference to  FIGS. 31 to 33 , for example. Thereafter, a semiconductor device is completed by performing the processes that have been described with reference to  FIGS. 13 to 28 .