In view of the fact that little analysis of the mechanism for the achievement of high resolution or a high aspect ratio in the thick-film resist process has been performed, we study development properties with respect to differences between the development methods employed for pattern formation using thick-film resist. This study identifies the most effective development method for thick-film resist and reports the mechanism of development. For this investigation, we use a development rate measurement system, a mask aligner, and lithography simulator to examine the dipping development method, the step puddle development method, the vibration development method, and the reverse development method. We employ a thick-film positive resist composed of diazo-naphthoquinone (DNQ) and Novolak resin, which is coated on a silicon substrate to a thickness of 24 micrometers . After pre-baking, the coated substrate is placed in a vacuum dessicator to remove water, followed by immersion in deionized water for a fixed period. A mask pattern is transferred to the resist coated substrate with a Mask Aligner Q4000 made by Quintel Corporation, and then the rate of development is measured. A laser microscope analysis of the result indicates that the step puddle development method gives the highest pattern resolution and sharpness, followed by the vibration development method, the dipping development method, and lastly the reverse development method. The mechanisms of the development are studied by comparing the development contrast and the energy of activation involved in each development method, and by conducting resist pattern simulations. The results indicate that the factors responsible for retarding the progression of the development process and causing a degradation of pattern profile and resolution are development inhibition due to N2 released from inside the resist during the development process, and due to products that are dissolved in the development solution.