This post explains for the semiconductor FS23N15D.
The Full Part Number is IRFS23N15D. The package is D2pak type.
The function of this semiconductor is 150V, HEXFET Power MOSFET.
The manufacturers of this product is International Rectifier.
See the preview image and the PDF file for more information.
Preview images :
High frequency DC-DC converters
1. Low Gate-to-Drain Charge to Reduce Switching Losses
2. Fully Characterized Capacitance Including Effective COSS to Simplify Design, (See App. Note AN1001)
3. Fully Characterized Avalanche Voltage and Current