A device for heating target tissue comprises a housing, an array of ultrasound transducers and a deflector member. The housing includes a tissue contacting surface. The array of ultrasound transducers is mounted within the housing on an array surface shaped so that ultrasound energy from the transducers converges on a target area a predetermined depth from the tissue contacting surface. The deflector member is located at a selected position within a field through which a portion of the ultrasound energy generated will pass on its way to the target area. The deflector member refracts a selected portion of the ultrasound energy to control a distance of separation between the array and a proximal edge of a region at which a level of ultrasound energy exceeds a predetermined threshold level.