BOI Local Controller described a landing event involving a military flight and an air carrier operating on closely spaced parallel runways that resulted in a TCAS RA received by the air carrier.

Narrative

Air carrier was inbound on a visual approach to Runway 28R and cleared to land. A flight of 4 VFR military fighter aircraft; were in formation inbound to Runway 28L for an overhead approach with a south break at 4;500 feet. Air carrier was told about the flight in a traffic call and told that the flight would be breaking south for Runway 28L. Military aircraft checked on the Tower frequency with the air carrier in sight and was cleared to land on Runway 28L and I reiterated that the air carrier aircraft was on final for Runway 28R. I then went back to air carrier and advised the pilot that the military flight had him in sight. Air carrier said that they had a TCAS/RA because of the military aircraft. The weather was VFR and wake turbulence not a factor. Our runways are 700 feet apart. The pilot of the air carrier told the Supervisor that the RA they received commanded a descent on very short final and the pilot knew they could not go around. Recommendation; as a general practice working Radar at BOI; I never use the 500 feet separation allowed per the 7110.65 between IFR and VFR aircraft. I always use 1000 feet because of the sensitivity of TCAS. In this case had I been the Radar Controller; I would have restricted the military aircraft 1000 feet above the air carrier until the break.