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2013-080033 (U.S. Pat. No. 8,574,817) and JP-A 2013- 083821 (U.S. Pat. No. 8,846,303). 

[0108] Typical of the acid labile group are groups of the following formulae (AL-1) to (AL-3). 

[0109] In formulae (AL-1) and (AL-2), RL 1 and RL 2 are each independently a C$_{1 }$-C$_{40 }$hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. The hydrocarbyl groups may be saturated or unsaturated and straight, branched or cyclic. Of the hydro› carbyl groups, C$_{1 }$-C$_{40}$ , especially C $_{1 }$-C$_{20 }$ alkyl groups are preferred. In formula (AL-1), "a" is an integer of Oto 10, preferably 1 to 5. 3 4 

[0110] In formula (AL-2), RL and RL are each indepen› dently hydrogen or a C$_{1 }$-C$_{20 }$hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. The hydrocarbyl groups may be saturated or unsaturated and straight, branched or cyclic. Of the hydro› carbyl groups, C$_{1 }$-C$_{20 }$alkyl groups are preferred. Any two of RL 2 , RL $^{3 }$and RL $^{4 }$may bond together to form a ring, typically alicyclic, with the carbon atom or carbon and oxygen atoms to which they are attached, the ring containing 3 to 20 carbon atoms, preferably 4 to 16 carbon atoms. 5 6 

[0111] In formula (AL-3), RL , RL and Rn are each independently a C$_{1 }$-C$_{20 }$hydrocarbyl group which may con› tain a heteroatom such as oxygen, sulfur, nitrogen or fluo› rine. The hydrocarbyl groups may be saturated or unsatu› rated and straight, branched or cyclic. Of the hydrocarbyl groups, C$_{1 }$-C$_{20 }$alkyl groups are preferred. Any two of RL 5 , RL 6 and RL 7 may bond together to form a ring, typically alicyclic, with the carbon atom to which they are attached, the ring containing 3 to 20 carbon atoms, preferably 4 to 16 carbon atoms. 

[0112] The base polymer may further comprise recurring units (b) having a phenolic hydroxyl group as an adhesive group. Examples of suitable monomers from which recur› ring units (b) are derived are given below, but not limited thereto. Herein RA is as defined above. 

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[0113] Further, recurring units ( c) having another adhesive group selected from hydroxyl (other than the foregoing phenolic hydroxyl), lactone ring, sultone ring, ether bond, ester bond, sulfonate bond, carbonyl, sulfonyl, cyano, and carboxyl groups may also be incorporated in the base polymer. Examples of suitable monomers from which recur› ring units ( c) are derived are given below, but not limited thereto. Herein RA is as defined above. 

