68  US 7,410,747  B2  67  10.  The positive resist composition as claimed in claim  1,  which further comprises a surfactant.  11.  The positive resist composition as claimed in claim  1,  wherein the compound (B) includes (Bl) a compound of  generating an organic sulfonic acid under the action of actinic  rays or radiation.  12.  The positive resist composition as claimed in claim  11,  which further comprises (B2) a compound of generating a  carboxylic acid under the action of actinic rays or radiation.  13.  The positive resist composition as claimed in claim  1,  which further comprises a solvent.  14.  The positive resist composition as claimed in claim  13,  wherein the solvent includes a propylene glycol monomethyl  ether acetate.  15.  The positive resist composition as claimed in claim  14,  wherein the solvent further includes a propylene glycol  monomethyl ether.  16.  The positive resist composition as claimed in claim  1,  wherein the actinic rays or radiation is selected from the  group consisting of electron beam, X-ray or EUV.  17.  A pattern forming method comprising forming a resist  film by using the positive resist composition claimed in claim  18.A  positive resist composition comprising: (A) a resin of  which solubility in an alkali developer increases under the  action of an acid, the resin containing a repeating unit repre› sented by formula (I) and a repeating unit represented by  formula (Ile); and (B) a compound capable of generating an  acid upon irradiation with actinic rays or radiation:  1;  and exposing and developing said resist film.  wherein  R$_{1 }$ represents a hydrogen atom, a methyl group, a cyano  group, a halogen atom or a perfluoro group,  R$_{2 }$ represents a non-acid-decomposable group which con› tains an oxygen atom, and when n represents an integer  of2 to 4, a plurality ofR$_{2}$s may be the same or different,  X represents a hydrogen atom or an organic group, and  when m represents an integer of2 to 4, a plurality ofXs  may be the same or different,  m represents an integer of 1 to 4, and  n represents an integer ofl to 4, provided that 2~n+m~5;  wherein formula (Ile) has the following structure:  R$_{3 }$ to R$_{5 }$ each independently represents a hydrogen atom, a  fluorine atom, a chlorine atom, a cyano group or an alkyl  group, and  X$_{1 }$represents a hydrogen atom or an organic group.  8.  The positive resist composition as claimed in claim  1,  wherein at least one ofX in formula (I) contains an alicyclic  structure and an aromatic ring structure or both an alicyclic  structure and an aromatic ring structure.  9.  The positive resist composition as claimed in claim  wherein the non-acid-decomposable group represented by R$_{2 }$ in formula (I) is an alkoxy group.  wherein  RII_$_{2 }$ represents an alkyl group, a cycloalkyl group, a halogen  atom, an aryl group, an aralkyl group, an alkoxy group or an  wherein  RII- 2  each independently represents an alkyl group, a  cycloalkyl group, a halogen atom, an aryl group, an  aralkyl group, an alkoxy group or an acyloxy group, and  said alkyl group and said aralkyl group each may have an  intervening linking group represented by-O-, -S-,  --CO$_{2}$-, --CO-, -SO 2 - or -SO-, and when s"  represents an integer of2 to 4, a plurality ofRII_$_{2}$s may be  the same or difference, and a plurality of  RII- $_{2}$s  may  combine with each other to form a ring structure,  X $^{1 }$and X$^{2 }$each independently represents a hydrogen atom  or an organic group,  v represents 0 or 1, and  s" represents an integer of0 to 4.  7. The positive resist composition as claimed in claim  1,  wherein the resin (A) further contains a repeating unit repre- sented by formula (III):  wherein  OMO  (Ila!)  +-,  ~  Q CH2  v  (R11-2),•-- 0X1  (Ile!)  0  (I)  (III)  R3  Rs  I  I  ----t  c-q- I  I  Ri  C02-X1 