A method of forming a CMOS device and a GaN PA structure on a 100 Si substrate having a surface orientated in 111 direction and the resulting device are provided. Embodiments include forming a device with a protective layer over a portion of a Si substrate; forming a V-shaped groove in the Si substrate; forming a buffer layer, a GaN layer, an AlGaN layer and a passivation layer sequentially over the Si substrate; forming trenches through the passivation and the AlGaN layers; forming second trenches through the passivation layer; forming electrode structures over portions of the passivation layer and filling the first and second trenches; removing portions of the passivation layer, the AlGaN layer and the GaN layer outside of the V-shaped groove down to the buffer layer; forming a dielectric layer over the Si substrate; and forming vias through the dielectric layer down to electrode structures and the device.