Abstract: A critical dimension (CD) vernier apparatus, appropriate for scanning electron microscope (SEM) measurements, formed with additional encoding patterns. A central strip pattern is disposed along a specific direction. A first plurality of strip patterns is disposed in parallel along the specific direction and at a first side adjacent to the central strip pattern. A second plurality of strip patterns is disposed in parallel along the specific direction and at a second side adjacent to the central strip pattern. A plurality of recognition patterns is selectively added to the strip patterns whereby the central strip pattern, the recognition patterns, and the strip patterns at the first side and the second side form a specific figure to serve as a critical dimension vernier pattern. In addition, a novel critical dimension vernier, which is appropriate for measuring the compliance of contact hole dimensions to process parameters at a specific resolution is provided.