A metal-film microbolometer formed on a glass membrane suspended on a silicon substrate has been fabricated by the anisotropic etching technique. The rectangular glass membrane is supported by its four leads connected to the corners of an etched V-groove cavity. This structure allows flexible thermal management and sensitivity optimization of the bolometer for different kinds of application, with a trade-off between lead thermal impedance and device active area. Optimizations of the structure applied to both a focal-plane array and a single detector are interpreted. A thermal impedance as high as 4 × 10 5 °C/W with a response time of several milliseconds can be achieved. For a 320 μm x 320 μm detector, theoretical predictions give a responsivity and normalized detectivity of over 700 V/W and 10 9 cm √/Hz/W, respectively. For dimensions of 128 μm × 128 μm, suitable for a focal-plane-array detector, theory predicts a D* of 5.5 × 10 8. A discrepancy exists between the experiment and the theory, which is also discussed.