CMOS technology innovations over the last decades opened doors to the possibility of designing fully integrated systems in CMOS at THz frequencies. Small antenna sizes at THz frequencies make CMOS and silicon attractive for steerable 2D transmitter and receiver arrays. Previous works successfully showed THz-source arrays with the use of on-chip antennas [1-5]. However, it is still a challenge implementing such arrays that are frequency and phase locked, with significant radiated power and efficiency in standard CMOS without costly additions. In this work we propose a scalable radiating-transmitter approach in 65nm CMOS that achieves a radiated power of +5.4dBm at 0.3THz using only a 2×3 on-chip array, an EIRP of +22dBm and 5.1% of radiated-power-to-DC power efficiency.