Wafer map defect pattern recognition is valuable for root cause analysis and yield learning. Most of the previous studies on defect pattern recognition are based on supervised machine learning, in which labeled wafer maps are used to train a machine learning model for automatic classification. Some problems arise in this approach. First, there may be misclassification in the original labeled data, which makes it difficult to establish an accurate prediction model. Secondly, defect patterns that are not defined before will not be classified correctly. In this paper, we proposed a semi-supervised framework to deal with these problems. Labeled wafer maps are first used to train a prediction model, with likely misclassified data excluded. The prediction model is then used to classify unlabeled data. The remaining data that cannot be properly classified are then sent to an unsupervised learning algorithm to extract more defect patterns with enhanced labeling techniques. This proposed approach is validated with TSMC 811K database, in which we are able to define five new defect pattern types. Experimental results show that total 14 defect types can be recognized with overall accuracy of 94.37%.