The linear or branched, saturated hydrocarbon group pref› erably has 1 to 25 carbon atoms, more preferably 1 to 15, and still more preferably 4 to 10. 

Examples of the linear, saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, a 5 butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group and a decyl group. 

Examples of the branched, saturated hydrocarbon group include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbu- tyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpen- tyl group, a 3-methylpentyl group and a 4-methylpentyl group, but excluding tertiary alkyl groups. 

The linear or branched, saturated hydrocarbon group may have a substituent. Examples of the substituent include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, an oxygen atom (=0), a cyano group and a carboxy group. 

The alkoxy group as a substituent for the linear or branched saturated hydrocarbon group is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group or a tert-butoxy group, and most 25 preferably a methoxy group or an ethoxy group. 

Examples of the halogen atom as a substituent for the linear or branched, saturated alkyl group include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is preferable. 

Example of the halogenated alkyl group as a substituent for the linear or branched, saturated hydrocarbon group includes a group in which part or all of the hydrogen atoms within the aforementioned linear or branched, saturated hydrocarbon group have been substituted with the aforementioned halogen atoms. 

The cyclic saturated hydrocarbon group of 3 to 20 carbon atoms for R 6 ’, R 7 ’ and R 8 ’ may be either a polycyclic group or a monocyclic group, and examples thereof include groups in which one hydrogen atom has been removed from a mono- cycloalkane, and groups in which one hydrogen atom has been removed from a polycycloalkane ( e.g., a bicycloalkane, a tricycloalkane or a tetracycloalkane ). More specific examples include groups in which one hydrogen atom has been removed from a monocycloalkane such as cyclopen› tane, cyclohexane, cycloheptane or cyclooctane; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane. 

The cyclic, saturated hydrocarbon group may have a sub- stituent. For example, part of the carbon atoms constituting the ring within the cyclic alkyl group may be substituted with a hetero atom, or a hydrogen atom bonded to the ring within the cyclic alkyl group may be substituted with a substituent. 

In the former example, a heterocycloalkane in which part of the carbon atoms constituting the ring within the afore› mentioned monocycloalkane or polycycloalkane has been substituted with a hetero atom such as an oxygen atom, a sulfur atom or a nitrogen atom, and one hydrogen atom has been removed therefrom, can be used. Further, the ring may contain an ester bond (----C( =0 )---0-) in the ring structure thereof. More specific examples include a lactone-containing monocyclic group, such as a group in which one hydrogen atom has been removed from y-butyrolactone; and a lactone› containing polycyclic group, such as a group in which one hydrogen atom has been removed from a bicycloalkane, tri› cycloalkane or tetracycloalkane containing a lactone ring. 

In the latter example, as the substituent, the same substitu› ent groups as those for the aforementioned linear or branched alkyl group, or an alkyl group of 1 to 5 carbon atoms can be used. 6 7 8 

Alternatively, R ’, R ’ and R ’ may be a combination of a linear or branched alkyl group and a cyclic group. 

Examples of the combination of a linear or branched alkyl group with a cyclic alkyl group include groups in which a cyclic alkyl group as a substituent is bonded to a linear or branched alkyl group, and groups in which a linear or branched alkyl group as a substituent is bonded to a cyclic alkyl group. 

Examples of the linear aliphatic unsaturated hydrocarbon group for R 6 ’, R 7 ’ and R 8 ’ include a vinyl group, a propenyl group ( an ally 1 group) and a butyny 1 group. 

Examples of the branched aliphatic unsaturated hydrocar› bon group for R 6 ’, R 7 ’ and R 8 ’ include a 1-methylpropenyl group and a 2-methylpropenyl group. 

The aforementioned linear or branched, aliphatic unsatur- ated hydrocarbon group may have a substituent. Examples of substituents include the same substituents as those which the aforementioned linear or branched alkyl group may have. 7 8 

Among the aforementioned examples, as R ’ and R ’, in terms of improvement in lithography properties and shape of the resist pattern, a linear or branched, saturated hydrocarbon group of 1 to 15 carbon atoms or a cyclic saturated hydrocar- bon group of 3 to 20 carbon atoms is preferable. 1 

The aliphatic hydrocarbon group for R may be either a saturated hydrocarbon group (that is, alkyl group), or an unsaturated aliphatic hydrocarbon group. Further, the ali› phatic hydrocarbon group may be chain-like or cyclic. The chain-like aliphatic hydrocarbon group may be linear or branched. The cyclic aliphatic hydrocarbon group may be either a polycyclic group or a monocyclic group. 

In the aliphatic hydrocarbon group, part of the carbon atoms constituting the aliphatic hydrocarbon group may be substituted with a substituent group containing a hetero atom, or part or all of the hydrogen atoms constituting the aliphatic hydrocarbon group may be substituted with a substituent. 

With respect to the substituent containing a hetero atom for substituting part of the carbon atom constituting the aliphatic hydrocarbon group, a hetero atom is an atom other than carbon and hydrogen, and examples thereof include an oxy› gen atom, a nitrogen atom, a sulfur atom and a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, an iodine atom and a bromine atom. 

The substituent group containing a hetero atom may be a group consisting of a hetero atom, or may be a group contain› ing a group or atom other than a hetero atom. 

Specific examples of the substituent group for substituting part of the carbon atoms include -0-, -C(=O)---0-, ----C(=O)-, ---0----C(=O)---O-, -C(=O)-NH-, -NH-(wherein the H may be substituted with a substituent such as an alkyl group or an acyl group), -S-, -S(=O)$_{2}$ - and -S(=O)$_{2}$---0-. When the aliphatic hydrocarbon group is cyclic, the aliphatic hydrocarbon group may contain any of these substituent groups in the ring structure. 

Specific examples of the substituent for substituting part of the hydrogen atom constituting the aliphatic hydrocarbon group, include an alkoxy group, a halogen atom, a haloge› nated alkyl group, a hydroxy group, an oxo group (=0), a cyano group, an aryl group, an alkoxyalkyloxy group, an alkoxycarbonylalkyloxy group, a carboxy group, ----eoo-z+ (wherein z+ is the same as defined above), ----C(=O)-O- R 6 ’, -O----C(=O)-R 7 ’ and-O-R 8 ’. EachofR 6 ’, R 7 ’ and R 8 ’ independently represents a linear or branched saturated hydrocarbon group of 1 to 25 atoms, a cyclic saturated hydro- 

