In this work, we present the simulation results for nitride-based fin-shaped field-effect transistors (FinFETs) using a technology computer-aided design (TCAD) device simulator. The FinFET has received attention for its applications in replacing high electron mobility transistors (HEMTs). AlGaN/GaN-based devices have outstanding electrical performances because of their high carrier density and high electron mobility in the two-dimensional electron gas (2DEG). Therefore, AlGaN/GaN-based double heterojunction FinFET (DH-FinFET) has been designed with double 2DEG layers to improve the on-state current (I-ON). However, the designed device has a critical problem in suppressing the enhancement of the I-ON. This phenomenon is called the two-dimensional hole gas (2DHG) which is formed as the opposite polarization charge by the 2DEG. As compared with the AlGaN/GaN-based single channel FinFET (SC-FinFET) which has a current of 548 mA/mm, the I-ON value of the AlGaN/GaN-based DH-FinFET is similar value of 578 mA/mm. AlN is used to increase the I-ON value of the SC-FinFET and obtained I-ON value of 988 mA/mm. This value is higher than that of AlGaN/GaN-based SC-FinFET. For this reason, we proposed the AlN/GaN-based DH-FinFET to improve I-ON. AlN/GaN-based DH-FinFET which has a higher I-ON value at V-GS = 7 V than AlN/GaN-based SC-FinFET.